Obsolete, a.
Etymology: [L. obsoletus, p.p. of obsolescere. See Obsolescent.]
1. No longer in use; gone into disuse; disused; neglected; as, an obsolete word; an obsolete statute; -- applied chiefly to words, writings, or observances.
2. (Biol.)
Not very distinct; obscure; rudimental; imperfectly developed; abortive.
Syn. -- Ancient; antiquated; old-fashioned; antique; old; disused; neglected. See Ancient.
1 other Webster entry under this spelling
Obsolete, v. i.
To become obsolete; to go out of use. [R.] Fitzed. Hall.
Shades of meaning
Some of the oldest or most ancient words are not obsolete, as father, mother, etc. A word is obsolete which has quite gone out of reputable use; a word is archaic which is falling out of reputable use, or, on the other hand, having been obsolete, is taken up tentatively by writers or speakers of influence, so that it may perhaps regain its position as a living word; a word is rare if there are few present instances of its reputable use. Compare old.