underweight (adj.)

• bony
• flat
• gangling
• gangly
• gaunt
• gawky
• lank
• lanky
• lean
• lightweight
• meager
• net
• overweight
• rawboned
• scraggy
• scrawny
• skeletal
• skinny
• spare
• spidery
• spindly
• twiggy
• undersized
• weight