Entwine

Entwine is a keyword ability appearing on modal instants and sorceries, ie. ones with the "Choose one-" clause. As you play a spell with entwine, if you pay the cost associated with it, instead of choosing one of the modes of the spell, it functions as though you chose both.

Spells with Entwine originally appeared in Mirrodin.

From the Comprehensive Rules:

• 502.32. Entwine
  • 502.32a Entwine is a static ability that functions while the spell is on the stack. “Entwine [cost]” means “You may choose to use all modes of this spell instead of just one. If you do, you pay an additional [cost].” Using the entwine ability follows the rules for choosing modes and paying additional costs in rules 409.1b and 409.1f–h.
  • 502.32b If the entwine cost was paid, follow the text of each of the modes in the order written on the card when the spell resolves.