Rhymes with PATTERNslatternpattern noun pat??tern \??pat-??rn\ (Medical Dictionary)Medical Definition of PATTERN 1: a model for making a mold used to form a casting 2: a reliable sample of traits, acts, tendencies, or other observable characteristics of a person, group, or institution <patterns of behavior> 3: an established mode of behavior or cluster of mental attitudes, beliefs, and values that