Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
crassesco, ĕre, v. inch., to grow thick, to thicken, grow dense or hard, grow large or fat (post-Aug.; most freq. in Pliny the elder): turtures milio, etc., Col. 8, 9, 2: sues, Plin. 13, 18, 32, § 110: ceparum capita, id. 19, 6, 32, § 103: pili quadrupedibus senectute, id. 11, 39, 94, § 231: mel (opp. dilutum), id. 11, 13, 13, § 32; cf.: vinum vetustate, id. 23, 1, 22, § 40: aër in nubes, id. 2, 43, 44, § 114: crassescente limo, id. 33, 5, 26, § 86.