timeless

adj

1. Eternal.

   “When Worlds, that count his Circles now, unhing’d, (Fate the loud Signal sounding) headlong rush To timeless Night and Chaos, whence they rose.”

2. Not affected by time; ageless.
3. (obsolete)Done at an improper time; unseasonable; untimely.

   “Must I behold thy timeless, cruel death?”

   “The lamp of day is quench’d beneath the deep, And soft approach the balmy hours of sleep: Nor fits it to prolong the heav’nly feast Timeless, indecent, but retire to rest.”

4. Not decreasing over time in quality and appeal.

   “The cave carvings have a timeless beauty.”

5. Without a time limit; untimed.

   “a timeless cricket match”

6. Outside of time; extratemporal.

noun

1. A gene encoding an essential protein that regulates circadian rhythm, normally written in italics: timeless.