WordNet sense 1 (moving and bending with ease):

lissom, lissome, lithe, lithesome, slender, svelte, sylphlike

WordNet sense 2 (characterized by beauty of movement, style, form, or execution):

graceful

WordNet sense 3 ((used of e.g. personality traits) readily adaptable):

limber

WordNet sense 4 (capable of being changed):

flexible

WordNet sense 5 (able to flex; able to bend easily):

flexile