Wiktionary
up against
prep. 1 (context idiomatic English) Facing; challenging, or opposing. 2 In contact with, abut.
Usage examples of "up against".
The children, well wrapped up against the cold, were clearly enjoying the fifteen minutes of freedom from their studies.
They could perhaps prop it up against the house and read it from a suitable distance.
I once had a funny female assistant who kept brushing up against my suit.