obsolete

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. No longer in use: an obsolete word.
2. adj. Outmoded in design, style, or construction: an obsolete locomotive.
3. adj. Biology Vestigial or imperfectly developed, especially in comparison with other individuals or related species; not clearly marked or seen; indistinct. Used of an organ or other part of an animal or plant.
4. v. To cause to become obsolete.

Century Dictionary and Cyclopedia

1. Gone out of use; no longer in use: as, an obsolete word; an obsolete custom; an obsolete law. Abbreviated obsolete
2. In descriptive zoöl., indistinct; not clearly or sharply marked; applied to colors, faded, dim: as, an obsolete purple; applied to ornaments or organs, very imperfectly developed, hardly perceptible: as, obsolete striæ, spines, ocelli. It is often employed to denote the lack or imperfect development of a character which is distinct in the opposite sex or in a kindred species or genus. Synonyms Ancient, Old, Antique, etc. See ancient.
3. To become obsolete; pass out of use.
4. To make obsolete; render disused.
5. In botany, notingan organ which is rudimentary or scarcely apparent.

Wiktionary

1. adj. of words, etc. no longer in use; gone into disuse; disused or neglected (often by preference for something newer, which replaces the subject).
2. adj. biology Imperfectly developed; not very distinct.

GNU Webster's 1913

1. adj. No longer in use; gone into disuse; disused; neglected; ; -- applied chiefly to words, writings, or observances.
2. adj. (Biol.) Not very distinct; obscure; rudimental; imperfectly developed; abortive.
3. v. rare To become obsolete; to go out of use.

WordNet 3.0

1. adj. no longer in use