Obsolete a. : No longer in use; gone into disuse; disused; neglected; as, an obsolete word; an obsolete statute; -- applied chiefly to words, writings, or observances.

Obsolete a. : Not very distinct; obscure; rudimental; imperfectly developed; abortive.

Obsolete v. i. : To become obsolete; to go out of use.

Example:
How long will biodisel last before it becomes impractical or Obsolete?

Taxonomy
lete, Dictionary, adjective, disuse, Synonyms, word origin, Pronunciation, suh, leet, Biology, imperfectly, comparison, Obsolete Definition, species, ness, Houghton Mifflin Company, äb, free online English dictionary.

Defination from the web:
Obsolete - Definition of Obsolete at Dictionary.com a free online dictionary with pronunciation, synonyms, and translation of Obsolete. Word of the Day and Crossword Puzzles. ... a discarded or outmoded type; out of date: an obsolete battleship. 3. (of a linguistic form) no longer in ...