to accept a situation or decision you do not like because you cannot change it:
They've been told: take the lower interest rate, or lump it.
It's the law so you can like it or lump it.
to put two or more different people or things together and consider them as a single group, sometimes wrongly
lump something together
You can't lump the symptoms together and blame them all on stress.
lump somebody/something in with somebody
The danger is that people who pay their bills on time will be lumped in with those that don't.