Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Gĕraestus or -os, i, f., the principal town of Eubœa, near the promontory Geraestus or Geraestum, opposite to the promontory of Sunium, now Geresto, or, acc. to others, Kastri, Liv. 31, 45, 10; Mel. 2, 7, 9; Plin. 4, 12, 21, § 63 sq.