problem
Cross references: 1. mystery 1. prob.lem \'pra:b-l*m, 'pra:b-*m, -.lem\ n [ME probleme, fr. MF, fr. L problema, fr. Gk proble-ma, li]t., something thrown forward, fr. proballein to throw forward, fr. pro- forward + ballein to throw - more at PRO-, DEVIL 1a: a question raised for inquiry, consideration, or solution 1b: a proposition in mathematics or physics stating something to be done 2a: an intricate unsettled question 2b: a source of perplexity or vexation 2. problem aj 1: dealing with a problem of human conduct or social relationship 2: difficult to deal with
Webster's English Dictionary