acetylcholine /əˌsitəlˈkoʊlin/ noun1 •A neurotransmitter in humans and other animals. It is an ester of acetic acid and choline with chemical formula CH₃COOCH₂CH₂N⁺(CH₃)₃.Acetylcholine build-up in the body can be toxic. — 2020 formsacetylcholines