Provoke is a keyword ability.
Amy attacks with a Goblin Grappler. Ned controls a tapped Canyon Minotaur. When Goblin Grappler's ability goes on the stack, she can target Canyon Minotaur with it, forcing it to untap and block the Goblin Grappler.
- 702.38a. Provoke is a triggered ability. "Provoke" means "Whenever this creature attacks, you may choose to have target creature defending player controls block this creature this combat if able. If you do, untap that creature."
- 702.38b. If a creature has multiple instances of provoke, each triggers separately.