"A cusp is when you grip a protruding hold from the side so that your palm, which faces towards you, is in contact with the rock this allows you to pull towards your body as well as down..
At the climbing wall some rounded holds feel better with a cusp than with a more conventional straight on grip. A cusp also leaves more space to match the hold."
A guppy is like a cusp but your palm is facing away from you. I think.
