an old unit of length (one sun), approximately 3 centimeters
板を一寸（約三センチ）だけ削って調整した。
I shaved the board by one sun (about 3 cm) to adjust it.
このネジは一寸のずれで取り付け不良になることがある。
This screw can be improperly mounted with as little as one sun of misalignment.
a little, a bit; a short time or small amount (often used conversationally like 'a little')
一寸待ってください、今戻ります。
Please wait a moment; I'll be right back.
今日は一寸体調が悪いので、早く帰ります。
I'm feeling a little unwell today, so I'll go home early.
結果は一寸の差で勝敗が分かれた。
The result was decided by a tiny margin.
その話は一寸難しいが、ゆっくり説明するよ。
That topic is a bit difficult, but I'll explain it slowly.