Final answer:
The symbol used to indicate a dimension referring to the diameter of a hole is the Ø symbol.
Step-by-step explanation:
The symbol used to indicate a dimension referring to the diameter of a hole is the Ø symbol. This symbol is an uppercase letter o with a diagonal line through it, representing the diameter of a circle. For example, if a hole has a diameter of 5 cm, it can be represented as Ø5 cm.