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lying on one's belly; crawling on one's belly; belly crawl
赤ん坊が腹這いで頭を上げた。
The baby lifted her head while lying on her belly.
訓練生たちは低い鉄条網の下を腹這いで前進した。
The recruits crawled forward on their bellies beneath the low barbed wire.
負傷した登山者は救助隊が着くまで腹這いのままでいた。
The injured climber stayed in the prone position until the rescue team arrived.