The phrase "killer legs" is an idiomatic expression that means having attractive, well-shaped or impressive legs. It's often used to describe someone who has a great pair of legs and can be applied both to men and women.
Sentences with «killer legs»
For killer legs, you need to reach fatigue during leg exercises. (flippingfifty.com)
You've got killer legs and I adore those sunnies and the necklace you made! (suzannecarillo.com)
They want killer legs and an ass that «breaks the Internet» as quickly as possible but aren't too concerned with upper body development. (legionathletics.com)