1 wall /ˈwɑːl/ noun
plural walls
1 wall
plural walls
Learner's definition of WALL
: a structure of brick, stone, etc., that surrounds an area or separates one area from another
often used figuratively
see also climbing wall, fire wall, retaining wall, seawall
: the structure that forms the side of a room or building
: the outer layer of something that is hollow (such as a part of the body or of a plant)

back is to/against the wall

see 1back

climbing the walls

see 1climb

drive (someone) up a/the wall

: to make (someone) irritated, angry, or crazy

fly on the wall

see 3fly

go to the wall

US : to make every possible effort to achieve something, to win, etc.
British : to fail because of a lack of money

hit a/the wall

: to reach a point at which you find it very difficult or impossible to continue

the writing/handwriting is on the wall

or see/read the writing/handwriting on the wall
used to say that it is clear that something bad will probably happen soon

up against a/the wall

: in a very bad position or situation
2 wall /ˈwɑːl/ verb
walls; walled; walling
2 wall
walls; walled; walling
Learner's definition of WALL

wall in

[phrasal verb]
wall (something) in or wall in (something)
: to surround (something) with a wall or with something that is like a wall

wall off

[phrasal verb]
wall (something) off or wall off (something)
: to separate (something) from the area around it with a wall

wall up

[phrasal verb]
wall (something) up or wall up (something) : to close off (an opening) by filling it with stone, brick, etc.
wall (someone) up or wall up (someone) : to keep (someone) as a prisoner in an enclosed space