Other forms: justified; justifies; justifying
To justify is to make excuses for one's actions, like the dieter who has to justify the few tiny pieces of chocolate she's sneaked in between salads.
Anyone who has ever made excuses for his or her actions knows the meaning of justify, like the bank robber who justifies his latest heist by claiming he needs the bank's money to support his charitable foundation. He might think he's got a good reason for holding up the bank, but he's going to have a hard time convincing the bank's owner of his reason, or justification. To justify a line of text is to space it so that it lines up with the margin.