double (adj.)

c. 1300, "twice as much or as large," also "repeated, occurring twice," also "of extra weight, thickness, size, or strength; of two layers," from Old French doble (10c.) "double, two-fold; two-faced, deceitful," from Latin duplus "twofold, twice as much," from duo "two" (from PIE root *dwo- "two") + -plus "more" (see -plus).

From early 14c. as "having a twofold character or relation," also "consisting of two in a set together; being a pair, coupled." From mid-14c. as "characterized by duplicity." The earliest recorded use in English is c. 1200, in double-feast "important Church festival."

Double-chinned is from late 14c.; double-jointed, of persons, is by 1828. Military double time (1833) originally was 130 steps per minute; double quick (adj.) "very quick, hurried" (1822) originally was military, "performed at double time."

The photographic double exposure is by 1872. The cinematic double feature is by 1916. Double figures "numbers that must be represented numerically by two figures" is by 1833. Double-vision is by 1714. Double indemnity in insurance is by 1832; double jeopardy is by 1817. The baseball double play is by 1866.

Double trouble "twice the trouble" is by 1520s; in 19c. America it was the name of a characteristic step of a rustic dance or breakdown, derived from slave dancing on plantations. A double-dip (n.) originally was an ice-cream cone made with two scoops (1936); the figurative sense is by 1940. Double bed "bed made to sleep two persons" is by 1779. Double life "a sustaining of two different characters in life" (typically one virtuous or respectable, the other not) is by 1888.

double (v.)

c. 1200, doublen, "to make double; increase, enlarge, or extend by adding an equal portion, measure, or value to," from Old French dobler, from Latin duplare, from duplus "twofold, twice as much" (see double (adj.)). Intransitive sense of "to become twice as great" is from late 14c.

From mid-14c. as "to duplicate;" from late 14c. as "to repeat, do twice;" from c. 1400 in the transitive sense of "lay or fold one part of upon another." By 1540s as "to pass round or by." Sense of "turn in the opposite direction" is from 1590s. Meaning "to bend or fold" (a part of the body) is from early 15c.; to double up bodily is from 1814.

A blow on the stomach "doubles up" the boxer, and occasions that gasping and crowing which sufficiently indicate the cause of the injury .... [Donald Walker, "Defensive Exercises," 1840]

Meaning "to work as, in addition to one's regular job" is c. 1920, circus slang, from performers who also played in the band. Related: Doubled; doubling.

double (n.)

late 14c., "an amount twice as great, a twofold quantity or size," from double (adj.). From mid-15c. as "a duplicate copy, something precisely like another."

Sense of "a backward turn to escape pursuers" is from 1590s. Stage sense of "performer or singer fitted to supply the place of a principal in an emergency" is by 1800, originally in opera. The Hollywood stunt double is by 1945. Meaning "an alcoholic drink with twice as much liquor as usual" is by 1922 (double drink is from 1901).  Tennis sense of "game played by two on each side" is by 1884. Baseball sense of "a hit in which the batter safely reaches second base" is by 1938. In betting, double or nothing is by 1899 (double or quit is from 1570s).

double (adv.)

"twice, doubly," late 14c., from double (adj.). Double-dyed "twice dyed, deeply imbued," but usually figurative, "thorough, complete" is from 1660s. To see double "by illusion to see two images of the same object" is from 1650s.

To double check "check twice" is by 1958 (see check (v.1)). Related: Double-checked; double-checking. To double-space (v.) in typing is by 1905. Related: Double-spaced. To double book in reservations is by 1966. To double park "park (a vehicle) parallel to another on the side toward the street" is by 1917. Related: Double-parked; double-parking.

Definitions of double
double (adj.)
having more than one decidedly dissimilar aspects or qualities; "the office of a clergyman is twofold; public preaching and private influence"- R.W.Emerson; "every episode has its double and treble meaning"-Frederick Harrison;
a double (or dual) role for an actor
Synonyms: dual / twofold / two-fold / treble / threefold / three-fold
double (adj.)
consisting of or involving two parts or components usually in pairs;
a double (binary) star
an egg with a double yolk
double doors
duple (or double) time consists of two (or a multiple of two) beats to a measure
Synonyms: dual / duple
double (adj.)
twice as great or many;
the dose is doubled
ate a double portion
Synonyms: doubled / twofold / two-fold
double (adj.)
used of flowers having more than the usual number of petals in crowded or overlapping arrangements;
double chrysanthemums have many rows of petals and are usually spherical or hemispherical
double (adj.)
used of homologous chromosomes associated in pairs in synapsis;
Synonyms: bivalent
double (adj.)
large enough for two;
a double bed
a double room
double (adj.)
having two meanings with intent to deceive;
a sly double meaning
Synonyms: forked
double (v.)
increase twofold;
The population doubled within 50 years
Synonyms: duplicate
double (v.)
hit a two-base hit;
double (v.)
bend over or curl up, usually with laughter or pain;
He doubled and vomited violently
Synonyms: double over / double up
double (v.)
do double duty; serve two purposes or have two functions;
She doubles as his wife and secretary
double (v.)
bridge: make a demand for (a card or suit);
double (v.)
make or do or perform again;
double (n.)
a base hit on which the batter stops safely at second base;
he hit a double to deep centerfield
Synonyms: two-base hit / two-bagger / two-baser
double (n.)
a stand-in for movie stars to perform dangerous stunts;
his first job in Hollywood was as a double for Clark Gable
Synonyms: stunt man / stunt woman
double (n.)
someone who closely resembles a famous person (especially an actor);
he could be Gingrich's double
Synonyms: image / look-alike
double (n.)
a quantity that is twice as great as another;
36 is the double of 18
double (n.)
raising the stakes in a card game by a factor of 2;
I decided his double was a bluff
Synonyms: doubling
double (adv.)
two together;
some people sleep better double
double (adv.)
downward and forward;
he was bent double with pain
double (adv.)
to double the degree;
his eyes were double bright
Synonyms: doubly / twice