An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) No longer in effect or use; not operating or functioning.
2) No longer in existence; dead; extinct.

M.E., from O.Fr. defunct or directly from L defunctus "dead," literally "off-duty," from p.p. of defungi "to discharge, finish," from → de- "off, completely" + fungi "perform or discharge duty," from PIE root *bheug- "to enjoy" (cognates: Latin fructus).

Nâkâr, "disabled" (Dehxodâ), leterally "not working," from negation prefix nâ-, → un-, + kâr, kardan, → work

A comet that has lost its ability to emit dust and gas and no longer displays the classic cometary features of a nebulous coma and a tail, or a destroyed comet. Comet Pigott The asteroid (944) Hidalgo is considered by some to be a defunct comet because of its unusual orbit. Another case is the asteroid Phaethon.

→ defunct; → comet.