1 [uncountable and countable]
the act of not accepting, believing in, or agreeing with something [≠ acceptance]
What are the reasons for his rejection of the theory?
2 [uncountable and countable]
the act of not accepting someone for a job, school etc [≠ acceptance]:
They sent me a rejection letter.
a situation in which someone stops giving you love or attention:
He was left with a feeling of rejection and loss.