Unblocked Creature

An attacking creature becomes an unblocked creature during the declare blockers step of the combat phase if no creature blocks it. It remains an unblocked creature until an effect causes it to become blocked, it's removed from combat, it stops being a creature, its controller changes, or the combat phase ends. Unblocked creatures don't exist outside of the combat phase or before the declare blockers step. See rule 309, "Declare Blockers Step."