The difference between Ham and Overact

When used as verbs, ham means to overact, whereas overact means to act in an exaggerated manner.

Ham is also noun with the meaning: the region back of the knee joint.

check bellow for the other definitions of Ham and Overact

Ham as a noun (anatomy):

The region back of the knee joint; the popliteal space; the hock.
Ham as a noun (countable):

A thigh and buttock of an animal slaughtered for meat.
Ham as a noun (uncountable):

Meat from the thigh of a hog cured for food.

Examples:

"a little piece of ham for the cat"
Ham as a noun:

The back of the thigh.
Ham as a noun (internet, informal, uncommon):

Electronic mail that is wanted; mail that is not spam or junk mail.

Examples:

"ant spam"

Ham as a noun (acting):

An overacting or amateurish performer; an actor with an especially showy or exaggerated style.
Ham as a noun (radio):

An amateur radio operator.

Ham as a verb (acting):

To overact; to act with exaggerated emotions.

Overact as a verb (acting):

To act in an exaggerated manner.

Examples:

"He overacted his part."
Overact as a verb (obsolete, transitive):

To act upon, or influence, unduly.