what does the idiom "making faces" mean?

Answer 1

The human face is remarkably adept at various contortions, some humorous, some threatening, some pathetic, and so on.
In the usual idiomatic expression, "making faces" is used when someone is being made fun of behind their back, is showing disapproval of something or someone, or when one is merely acting like a buffoon. So, you would have to know the context.

Answer 2

Does that indeed qualify as an idiom?

According to www.dictionary.com: id·i·om ( P ) Pronunciation Key (d-m)
n.
A speech form or an expression of a given language that is peculiar to itself grammatically or cannot be understood from the individual meanings of its elements, as in keep tabs on.
The specific grammatical, syntactic, and structural character of a given language.
Regional speech or dialect.

A specialized vocabulary used by a group of people; jargon: legal idiom.
A style or manner of expression peculiar to a given people: “Also important is the uneasiness I've always felt at cutting myself off from my idiom, the American habits of speech and jest and reaction, all of them entirely different from the local variety” (S.J. Perelman).
A style of artistic expression characteristic of a particular individual, school, period, or medium: the idiom of the French impressionists; the punk rock idiom.

Answer 3

Manipulating your facial features to cause laughter when viewed by another.

Answer 4

fighting back or making funny or grumpy faces

Answer 5

:P....;).....:).......
expressing stupidity through different facial interpretations......ha ha ha ha..........