Set - definition of set by The Free Dictionary Set (sĕt) n Mythology Variant of Seth2 set 1 (sĕt) v set, set·ting, sets v tr 1 To put in a specified position or arrangement; place: set a book on a table; set the photo next to the flowers 2 a To put into a specified state: set the prisoner at liberty; set the house ablaze; set the machine in motion b To cause to begin an action: The