Synonyms for Chummy (same or very similar meaning)
WordNet sense 1 ((used colloquially) having the relationship of friends or pals):
pally, matey, palsy-walsy
WordNet sense 2 (characteristic of or befitting a friend):
friendly
WordNet sense 3 ((used informally) associated on close terms):
thick, buddy-buddy
WordNet sense 4 (close in relevance or relationship):
close
From the ODE community, based on WordNet
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