IPA: /ˈbreɪnˌstɔːrmər/
KK: /ˈbrɛnˌstɔrmər/
A person who generates ideas or solutions through brainstorming sessions.
During the meeting, she was the best brainstormer, coming up with several innovative ideas.
Brainstormer → It is formed from "brain" (from Old English "brægen", meaning the organ of thought) and "storm" (from Old English "styrman", meaning to disturb or agitate) combined with the suffix "-er" (meaning a person who). A brainstormer is a person who disturbs or agitates thoughts to generate ideas.
Think of someone using their 'brain' to 'agitate' or 'disturb' thoughts in order to come up with new ideas — that's what a brainstormer does.