costly (adj.) Copy link Outline 1. prĕtiōsus2. cārus • costly (adj.): 1. prĕtiōsus: v. precious. 2. cārus: v. dear. Or expr. with pretium: as, to be c., magni esse pretii, or magno pretio: v. price. Phr.: in a c. manner, pretiose, sumptuose: v. expensively.