Unattach
To move an Equipment away from the creature it’s attached to so that the Equipment is on the battlefield but is not equipping anything. See rule 701.3d.

Unblockable (Obsolete)
A term that meant "can’t be blocked." Cards that used this term have received errata in the Oracle card reference.

Unblocked Creature
An attacking creature once no creature has been declared as a blocker for it, unless an effect has caused it to become blocked. It remains an unblocked creature until it’s removed from combat or the combat phase ends, whichever comes first. See rule 509, "Declare Blockers Step."

Undaunted
A keyword ability that reduces the cost of a spell based on the number of opponents you have. See rule 702.124, "Undaunted."

Undying
A keyword ability that can return a creature from the graveyard to the battlefield. See rule 702.92, "Undying."

Unearth
A keyword ability that lets a player return a creature card from his or her graveyard to the battlefield. See rule 702.83, "Unearth."

Unflipped
A default status a permanent may have. See rule 110.6 and rule 709, "Flip Cards." See also Flipped.

Unleash
A keyword ability that allows a creature to enter the battlefield with a +1/+1 counter on it and stops it from blocking if it has a +1/+1 counter on it. See rule 702.97, "Unleash."

Unless
A word used to indicate a certain style of cost. See rule 117.12a.

Untap
To rotate a permanent back to the upright position from a sideways position. See rule 701.19, "Tap and Untap."

Untap Step
Part of the turn. This step is the first step of the beginning phase. See rule 502, "Untap Step."

Untap Symbol
The untap symbol in an activation cost means "Untap this permanent." See rule 107.6.

Untapped
A default status a permanent may have. See rule 110.6 and rule 701.19, "Tap and Untap." See also Tapped.

Upkeep Step
Part of the turn. This step is the second step of the beginning phase. See rule 503, "Upkeep Step."