What is the Latin word for monstrous?

The usual Latin words for “monstrous” are mōnstruōsus, prōdigiōsus, portentōsus. The right choice depends on the sense; see the distinctions below.

English → Latin

“monstrous” in Latin

mōnstruōsusstrange, preternatural, monstrous prōdigiōsusunnatural, strange; wonderful, marvellous, prodigious portentōsusfull of monsters

The English word monstrous itself goes back to Latin moneō, through monstrosus.

Riddle & Arnold A Copious and Critical English–Latin Lexicon, 1864

monstrous

PROP., monstrosus; prodigiosus; portentosus.

Figuratively, rationi repugnans (contrary to reason).

Quick answer

What is the Latin word for monstrous?: The usual Latin words for “monstrous” are mōnstruōsus, prōdigiōsus, portentōsus. The right choice depends on the sense; see the distinctions below.

Entry from J. E. Riddle & T. K. Arnold, A Copious and Critical English–Latin Lexicon (rev. C. Anthon, New York: Harper, 1864), digitised by Fergus J. P. Walsh, CC BY-SA 4.0; Latin markup adapted by latindictionary.co.