CHECKSIGVERIFY

Word: OP_CHECKSIGVERIFY
Opcode: 173
Hex: 0xad

CHECKSIGVERIFY, predictably, runs CHECKSIG, then VERIFY.
CHECKSIG: The entire transaction's outputs, inputs, and script are hashed.
The signature used by CHECKSIG must be a valid signature for this hash and public key. If it is, 1 is returned, 0 otherwise.
VERIFY marks transaction as invalid if top stack value is not true.