()つん()

よつんばい
noun
on all fours; crawling on hands and knees
body-part
1. on all fours; crawling position; hands and knees
The posture of being down on both hands and both knees, like a crawling baby or an animal. Used to describe the physical position itself.
The baby is crawling on all fours.
()つん()いになって、ベッド(した)(さが)した
I got on all fours and looked under the bed.
The ceiling inside the dark tunnel was so low that we could only move forward on all fours.

()つん()い describes the posture of being on all fours — both hands and both knees on the ground. Comes from ()つ (four) + ()い (crawling).

Common patterns

Usage

Describes a physical posture, not a movement verb. Typically used with なる (to assume the position) or で (while in the position). Common contexts include babies crawling, searching under furniture, or moving through low spaces.