Botox: A highly purified preparation of botulinum toxin A, a toxin produced by the bacterium Clostridium botulinum. Botox is for injection, in very small amounts, into specific muscles. It acts by blocking the transmission of nerve impulses to muscles and so paralyzing the muscles. Botox is a brand name that has passed into popular usage as a synonym for Botulinum toxin.

Botox treatment has found a growing number of uses from easing muscle spasms (as, for example, in spastic cerebral palsy) to its increasingly widespread cosmetic use in flattening wrinkles.