Etymology
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vertical (adj.)
Origin and meaning of vertical

1550s, "of or at the vertex, directly overhead," from French vertical (1540s), from Late Latin verticalis "overhead," from Latin vertex (genitive verticis) "highest point" (see vertex). Meaning "straight up and down" is first recorded 1704. As a noun meaning "the vertical position or line" from 1834. Related: Vertically.

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lean (n.1)
"action or state of leaning, deviation from a vertical position," 1776, from lean (v.).
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rock-face (n.)

"vertical expanse of natural rock," 1847, from rock (n.1) + face (n.).

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plumb (adj.)

"perpendicular, vertical, true according to a plumb-line," mid-15c., plom, from plumb (n.). As an adverb, "in a vertical direction, straight down," c. 1400. The notion of "exact measurement" led to the extended adverbial sense of "completely, downright" (1748), sometimes spelled plump, plum, or plunk.

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paling (n.)

"fence formed by connecting pointed vertical stakes by horizontal rails above and below," 1550s, from pale (n.).

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stabilize (v.)
1861, originally of ships; probably a back-formation from stability, or else from French stabiliser. Related: Stabilized; stabilizing. Earlier verbs in the same sense were stabilitate (1640s) and simple stable (v.) "make steady or firm, make stable" (c. 1300), from Old French establir.
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plumb-line (n.)

"a cord or line with a metal bob attached to one end, used to determine vertical direction," mid-15c., from plumb (n.) + line (n.).

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liftoff (n.)
also lift-off, "vertical take-off of a rocket, etc.," 1956, American English, from the verbal phrase, from lift (v.) + off (adv.). Earlier, of aircraft, simply lift (1879). Figurative use from 1967.
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bluff (n.1)
"broad, vertical cliff," 1680s, from bluff (adj.) "with a broad, flat front" (1620s), a sailors' word, probably from Dutch blaf "flat, broad." Apparently a North Sea nautical term for ships with broad bows and flat vertical stems. It was later extended to landscape features in North America, such as high broad banks along a shore or range of hills. Of persons, in reference to a full face, indicative of frankness and rough good humor, 1808.
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perpendicular (adj.)

late 15c., perpendiculer, of a line, "lying at right angles to the horizon" (in astronomy, navigation, etc.), from an earlier adverb (late 14c.), "at right angles to the horizon," from Old French perpendiculer, from Late Latin perpendicularis "vertical, as a plumb line," from Latin perpendiculum "plumb line," from perpendere "balance carefully," from per "thoroughly" (see per) + pendere "to hang, cause to hang; weigh" (from PIE root *(s)pen- "to draw, stretch, spin").

The meaning "perfectly vertical" is by 1590s. As a noun, "a line that meets another line or plane at right angles," from 1570s. The earlier noun was perpendicle (c. 1400). Related: Perpendicularly; perpendicularity.

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