Term (a verb) for (giving) a laugh that is a short and dry reaction when hearing something unrealistic

Question

Is there a verb to express that short expulsion of air through the nose while you smile a bit? It isn't really a laugh, but more of a reaction. It could be something you do when you hear something you don't agree with. Like imagining a situation and then thinking

Yea, like that's gonna happen.

I initially thought scoffed, but I'm not sure anymore by the definitions I've read.

Would it make sense to use it as follows:

She's a strong girl. I couldn't help but scoff at the thought of someone hurting her.

Answer 1

To scoff is to express derision, but not only by making a sound with the mouth or nose. One can scoff in many ways. Possibly you could use 'snort'.

SNORT
VERB
[NO OBJECT]
Make a sudden explosive sound through one's nose, especially to express indignation or derision.

‘she snorted with laughter’

I was one of the people who snorted with derision when Gwyneth Paltrow spoke of "consciously uncoupling" with husband Chris Martin.

Snort (Oxford Dictionaries)

Answer 2

The word you are looking for dry reaction (of smile/laugh) is Sardonic. When you're being sardonic, or if you have a sardonic laugh or smile, you're making fun of someone or something in a mean, bitter way. The sardonic is define by Meriam Webster as:

Merriam Webster

showing that you disapprove of or do not like someone or something : showing disrespect or scorn for someone or something

Or Oxford Dictionaries

Grimly mocking or cynical.

Usage: "If she went down in trousers he would give one of those sardonic laugh."

There are nearly 17,000 other citation of sardonic laugh from Google books.

And, there are nearly 223,000 other citation of sardonic smile from Google books