From Longman Dictionary of Contemporary Englishat half-mastat half-masta) MIDDLEif a flag is flying at half-mast, it has been raised to the middle of the pole in order to show respect and sadness for someone who has died b) British English humorousSHORT/NOT LONG if a piece of clothing is at half-mast, it is lower down the body than is usual → half-mast
