Verb:
1)Somthing you look up in Urban Dictionary when your uncreative brain isn't able to figure out a better definition to look up. As "look up" is written next to the look-up-box.
2) Something you did a few seconds ago,of course after giving this definition a thumb up.

antonym: look down

To search online, in a book, magazine, dictionary, encyclopedia, other writing work, for an answer or other need

i am good and fun

to look up

to look up as in to look into the sky retard.

Someone looked this up in an attempt to see if anytone was smarter than them by already adding it.

What it usualy says before a search box on a dictionary website (on the other side from the search button)