1To scatter or sprinkle something — water, salt, sand, powder, beans, etc. — over an area. Used in everyday expressions like 庭に水をまく ("water the garden") and 豆をまく ("throw beans" at the Setsubun festival). Because 撒 is outside the jōyō kanji list, the verb is usually written in kana. When sowing seeds to grow plants, the distinct kanji 蒔く is used instead.
夏の夕方、涼しくするために打ち水をまいた。
On a summer evening, I sprinkled water on the ground to cool things down.
節分の日、家族みんなで「鬼は外、福は内」と言いながら豆をまいた。
On Setsubun, the whole family threw beans while shouting "Demons out, fortune in!"
雪道が滑らないように、玄関の前に塩をまいた。
I scattered salt in front of the entrance so the snowy walkway wouldn't be slippery.
工事現場では砂ぼこりが立たないよう、定期的に水を撒いている。
At the construction site, they regularly sprinkle water to keep dust from rising.
2To hand out or distribute flyers, leaflets, business cards, etc. — usually broadcasting them broadly to many people rather than handing them out one-by-one. Carries a "scattering / blanketing" nuance, more aggressive than the neutral 配る.
駅前で新しいお店のチラシをまいた。
We handed out flyers for the new shop in front of the station.
選挙運動でビラをまく学生ボランティアが集まった。
Student volunteers gathered to hand out flyers for the election campaign.
3To shake off or give the slip to someone who is following you — a tail, a stalker, an annoying companion — by losing them in the crowd or with evasive maneuvers. Familiar from spy and crime fiction, but also used casually, e.g. 「うっとうしい人をまく」 "ditch someone annoying."
尾行に気づいたスパイは、人混みにまぎれて巧みに相手をまいた。
Realizing he was being tailed, the spy skillfully shook off his pursuer by blending into the crowd.
しつこく付きまとってくる男を、駅で電車を乗り換えてまいた。
I shook off the guy who kept following me by switching trains at the station.