1.
If you ~ a fact or a piece of information, you find it out by looking in something such as a reference book or a list.
I looked your address up in the personnel file...
Many people have to ~ the meaning of this word in the dictionary.
PHRASAL VERB: V n P, V P n (not pron)
2.
If you look someone up, you visit them after not having seen them for a long time.
I’ll try to look him up, ask him a few questions...
She looked up some friends of bygone years.
= visit
PHRASAL VERB: V n P, V P n (not pron)
3.
If a situation is looking up, it is improving. (INFORMAL)
Things could be looking up in the computer industry.
= improve
PHRASAL VERB: usu cont, V P