luò​wǔ

fall behind

落伍 luò​wǔ
fall behind verb
to fall behind the ranks or a group moving together

During the march, he fell behind because he lacked the physical strength to keep up.

outdated verb
to be behind the times or obsolete in thinking or style

If you don't learn new things, you will soon fall behind the times.

Frequency

Movie subtitles
2.12 per million appears in 1% of films
Written text
1.95 per million

Sources

Definitions
CC-CEDICT