'Intimidate' was introduced in the Zendikar block. It is a color shift for the original ability Fear.

702.11. Intimidate

• 702.11a. Intimidate is an evasion ability.
• 702.11b. A creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it. (See rule 509, "Declare Blockers Step.")
• 702.11c. Multiple instances of intimidate on the same creature are redundant.

Translation:

• 702.11a - Intimidate applies to combat in defining who can and can't block the creature.
• 702.11b - Your opponent can only block this creature by using an artifact creature or a creature that shares this creature's color.
• 702.11c - The game doesn't care how many instances of Intimidate a creature has, 1 is the same as 100.