زيت doesn't appear in Hans Wehr's Modern Standard Arabic dictionary, but Lane's Arabic-English Lexicon has 2 entries for it, distinguished by diacritics. Select one below for the full classical Arabic definition.

• زَاتَهُ Form 1

  1 زَاتَهُ ذ , aor. يَزِيتُهُ, [inf. n. زَيْتٌ,] He anointed him, or it, with زَيْت, i. e. oil of the زَيْتُون [or olive]. (Msb.) You say, زِتٌّ, meaning I anointed my head, and the head of another, with oil of the زيتون.…

  View in Lane's Lexicon →

• زَيْتٌ

  زَيْتٌ ذ The oil, (S, Mgh, Msb, K,) or expressed juice, (M, TA,) or مُخّ [i. e. best, or choicest, of the constituents], (A, TA,) of the زَيْتُون [or olive]. (S, M, A, Mgh, Msb, K.) [In the present day it is applied to A…

  View in Lane's Lexicon →