fall behind

Verb

fall behind (third-person singular simple present falls behind, present participle falling behind, simple past fell behind, past participle fallen behind)

1. Used other than figuratively or idiomatically: see fall, behind.
2. (idiomatic, intransitive) To be late (for a regular event)
   • You're falling behind with the rent.
3. (intransitive) To be progressively below average in performance.
   • You could lose your job if you keep falling behind with your work.
   • It's not like John to fall behind in maths.
4. (intransitive, transitive) to fail to keep up (with)