ETYM Old Eng. warant, Old Fren. warant a warrant, a defender, protector, French garant, originally a p. pr. pf German origin, from Old High Germ. weręn to grant, warrant, German gewähren; akin to OFries. wera. Related to Guarantee.
An authorization allowing police to perform specified acts.

1. To make secure; to give assurance against harm; to guarantee safety to.
2. To give assurances or proof; to justify; to maintain; to sanction.
3. To give a guarantee or warranty to; to assure as if by giving a warrant to.
4. To secure to, as a grantee, an estate granted; to assure.