Understand  v. (past and past part. -stood) 1 perceive the meaning of (words, a person, a language, a subject, etc.) (understood you perfectly; cannot understand algebra). 2 perceive the significance or cause of (do not understand why he came). 3 (often absol.) Sympathize with, know how to deal with (quite understand your difficulty; ask her, she understands). 4 (often foll. By that or absol.) Infer, take as implied (am i to understand that you refuse?; he is old, i understand).