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to cut into (a line, conversation, etc.); to force oneself into (e.g. a crowd); to wedge oneself into; to squeeze oneself into; to intrude on; to interrupt
to fall below (of stock prices, sales, etc.); to drop below
狭い隙間にわり込むように車を停めた。
I parked the car by squeezing into a narrow gap.
彼は議論の最中にわり込んだ。
He cut into the discussion midway.
見知らぬ人が行列にわり込んでいる。
A stranger is cutting into the line.