Somewhat like or resembling cannibalism; having qualities suggestive of cannibalistic behavior.
From 'cannibal' plus the suffix '-ish' (meaning somewhat or having the quality of). The '-ish' suffix is productive in English for creating approximate adjectives.
Adding '-ish' to something transforms it into 'sort of like that thing'—so 'cannibalish' means 'kind of like cannibalism'—a linguistic softening effect!
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