(n.) 1. A disk tumbler with “V” shaped notches in its sides that do not allow operation.
(n.) 2. A lever tumbler which has “V” shaped notches in the contact end near the gate.
(n.) 3. A pin tumbler with “V” shaped grooves around its circumference.
(n.) 4. A combination wheel with “V” shaped notches along its outside diameter.

Source: Lock Industry Standards and Training (LIST) Council