dissent, disagree, reject, disallow
It is not "assent", but good guess. A synonym for agree is "consent." You should usually only use the phrase "I consent" in a formal situation. "Dissent" is the antonym of "consent." Remember, there is no such word as "assent," and you should only use the phrase "I consent" in a formal situation.
Nodding your head often is a sign of assent in society
The homophone for "assent" is "ascent."
She nodded in agreement to assent to their proposal.
she had to assent to comming to school on time
Assent as a verb: Assenting to her demands, I did as she requested. Assent as a noun: When told they were going to see The Avengers, Jayne nodded her assent.
I assent to your demands, sir.
A sailor's agreement or assent would be "aye."
his assent was bad
The team is seeking your official assent, but we'll go without it.
The child nodded in assent when asked if they wanted ice cream for dessert.
Dissent