IPA: /ˈpɪk.nɪ.kər/
KK: /ˈpɪk.nɪ.kər/
A person who enjoys eating outdoors, usually in a park or a similar place, often with friends or family.
We saw a picnicker enjoying lunch under the trees.
Picnicker → It is formed from "picnic" (from French *pique-nique*, meaning a meal eaten outdoors) and "-er" (meaning a person who). A picnicker is a person who enjoys having meals outdoors, typically in a park or natural setting.
Think of someone who enjoys having a meal outdoors — that's what a picnicker does.