What do you call the gesture when someone makes a sarcastic or parenthetical side-comment? It's usually something related to the original comment that's said quietly to someone else, sometimes sarcastic, sometimes secretive. In movies, the person puts their hand at an angle near their mouth and usually raise an eyebrow if it's sarcastic. I know there's a name for that kind of gesture -- anyone know what it is? I found "side remark" in the thesaurus but it doesn't have any words that indicate something quietly shared away from or about the source comment.
3 : slyly disparaging : insinuating < snide remarks >
Snide remarks are the kinds of things people say with a sneer on their face. When you leave a movie theater and your friend says, “I can't believe someone was actually paid to write that screenplay,” he's being snide.
Another possibility, which doesn't have the malicious connotation is to "interject"
- to interpose abruptly or sharply; interrupt with; throw in: she interjected clever remarks.
- to come between; interpose
- the act of interjecting.
- something interjected, as a remark.
- the utterance of a word or phrase expressive of emotion; the uttering of an exclamation.
- Grammar: any member of a class of words expressing emotion, distinguished in most languages by their use in grammatical isolation, as Hey! Oh! Ouch! Ugh! Any other word or expression so used, as Good grief! Indeed!
If the aside is meant to be heard by others, it could be a stage whisper
Any loud whisper intended to be overheard.
Oxford Dictionaries Online
TALKING OUT THE SIDE OF YOUR MOUTH see English Language & Usage
MUTTERING UNDER YOUR BREATH: Figure of speech [spoken] so softly that almost no one can hear it. (Typically: curse ~; curse some-one or something ~; mutter ~; mutter something ~; say something ~.) John was muttering something under his breath, and I don't think it was very pleasant. I'm glad he said it under his breath. If he had said it out loud, it would have caused an argument. See The Free Dictionary under breath
a sarcastic aside
(as HotLicks said)
One idiom is "Under h(er|is) breath.". This may connote a more resentful, anti-authoritarian sort of vibe than you're going for, though. As in:
"Eat your peas, Amanda; they're good for you."
"As if you'd eat them yourself," she muttered under her breath.