0 to try to find a piece of information by looking in a book or on a computer: --
If you don't know what the word means, look it up in a dictionary.
You could try looking him up in a dictionary of biography.
I had to look up the word 'possession' to check how to spell it.
Does anybody look up slang words in the dictionary?
The software looks up words automatically.
How can you look the word up if you don't know how to spell it?