The definition of a caveat is a warning.
(noun)An example of caveat is a police officer telling someone to stop or they'll shoot.
See caveat in Webster's New World College Dictionary
noun
Origin: L, let him beware; 3d pers. sing., pres. subj., of cavere, to beware, take heed: see hear
See caveat in American Heritage Dictionary 4
noun
Origin:
Origin: From Latin, let him beware
Origin: , third person sing. present subjunctive of cavēre, to beware
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