dormant (adj.)

late 14c., "fixed in place," from Old French dormant (12c.), present participle of dormir "to sleep," from Latin dormire "to sleep," from PIE root *drem- "to sleep" (source also of Old Church Slavonic dremati "to sleep, doze," Greek edrathon "I slept," Sanskrit drati "sleeps").

Meaning "in a resting situation, lying down with the head on the forepaws" (in heraldry, of beasts) is from c. 1500. Meaning "sleeping, asleep" is from 1620s. General sense of "in a state of rest or inactivity" is from c. 1600. Of volcanoes from 1760.

The Neapolitans are never so much afraid of this fiery Mountain as when its Flames lie, as 'twere, dormant ; for then it is that they live in constant Fear of a fresh huge Eruption, or, much worse, an Earthquake. [from the entry for "Vesuvius" in Brice's "Grand Gazetter Or Topographic Dictionary," 1760]

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Definitions of dormant from WordNet

dormant (adj.)
in a condition of biological rest or suspended animation;
dormant buds
Synonyms: hibernating / torpid
dormant (adj.)
lying with head on paws as if sleeping;
Synonyms: sleeping
dormant (adj.)
(of e.g. volcanos) not erupting and not extinct;
a dormant volcano
Synonyms: inactive
dormant (adj.)
inactive but capable of becoming active;
her feelings of affection are dormant but easily awakened
Synonyms: abeyant