1 : lacking grace in movement or posture; "a gawky lad with long ungainly legs"; "clumsy fingers"; "what an ungainly creature a giraffe is"; "heaved his unwieldy figure out of his chair"
2 : slow to learn or understand; lacking intellectual acuity; "so dense he never understands anything I say to him"; "never met anyone quite so dim"; "although dull at classical learning, at mathematics he was uncommonly quick"- Thackeray; "dumb officials make some really dumb decisions"; "he was either normally stupid or being deliberately obtuse"; "worked with the slow students"