Custom prayer candles. How to use custom in a sentence. . custom a practice followed as a matter of course among a people; a habitual practice of an individual: It is her custom to take a walk every night before dinner. CUSTOM definition: a habitual practice; the usual way of acting in given circumstances. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. Synonym Discussion of Custom. CUSTOM definition: 1. Easy Ordering. The meaning of CUSTOM is a usage or practice common to many or to a particular place or class or habitual with an individual. See examples of custom used in a sentence.