Simple past tense and past participle of chum.(verb)
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Use "chummed" in a sentence
"Simpson belonged, on whom Mr. Pickwick was 'chummed' in the"
"She got the candle, and burned it until one of the other girls looked in (you know she's not 'chummed' with anybody yet) and showed her where the push-button was in the wall."
"The men would alternate on an anchor watch and keep the fish "chummed" up during the night."