Lean, spare, lank, lanky, gaunt, rawboned, angular, scrawny, skinny mean thin because of absence of superfluous flesh.
Lean stresses the lack of fat and therefore of rounded contours.
Spare often suggests abstemiousness or sinewy strength.
Lank suggests tallness or length as well as leanness; often also it implies wasting.
Lanky adds the suggestions of awkwardness and loose-jointedness.
Gaunt stresses want of sufficient flesh to conceal the bones; it often connotes overwork or undernourishment.
Rawboned often equals gaunt, but it is applied particularly to persons of large, ungainly frame and it seldom implies undernourishment.
Angular implies not only absence of curves, but jerkiness or stiffness in movement.
Scrawny and skinny imply extreme thinness but scrawny may additionally suggest slightness or a shrunken meager quality while skinny suggests a stringy fleshless condition such as is associated with a deficiency of vitality or strength.