noun, noun or participle which takes 'suru'
falling behind; being left behind; dropping out
Figurative use: failing to keep up with a group, trend, or competition; often implies being left out or dropping out from a collective effort.
彼は競争に落伍してしまった。
He fell behind in the competition.
時代の変
I keep studying so as not to be left behind by the changing times.
noun, noun or participle which takes 'suru'
falling out of line; straggling from the ranks
Literal military or marching use: dropping out of formation or falling behind the ranks. Less common in everyday speech.
行軍中に落伍する兵士が出た。
Some soldiers fell out of line during the march.