the GNU version of the Collaborative International Dictionary of English
n. A person who knowingly utters falsehood; one who lies.
The Century Dictionary and Cyclopedia
n. One who lies; a person who knowingly utters falsehood; one who deceives by false report or representation.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a person who has lied or who lies repeatedly
Word Usage
"Because of the emotional impact of the label liar, be sure to label the behavior, not the child i.e., “What you said is a lie” versus “You are a liar!”"