aerodynamic
angular
beanstalk
bony
delicate
fine-boned
gangly
lank
lanky
lean
lissome
lithe
meager of body
narrow
rawboned
scraggy
scrawny
sinuous
skeletal
skin-and-bone
skinny
sleek
slender
slight
slightly-built
slim
small-boned
spare
spindly
spiny
streamlined
stringy
svelte
sylphlike
thin
trim
underdeveloped
underweight
waif-like
willowy
wiry
wispy