WordWeb Online

1. Relatively long in duration; tediously protracted
   "a prolonged and bitter struggle";
   - drawn-out, extended, lengthy, protracted, long-drawn-out
    
2. Drawn out or made longer spatially
   "a prolonged black line across the page";
   - elongated, extended, lengthened

1. Lengthen in time; cause to be or last longer
   "We prolonged our stay";
   - protract, extend, draw out
    
2. Lengthen or extend in duration or space
   "prolong the treatment of the patient";
   - sustain, keep up

See also: long

Type of: bear on, carry on, continue, lengthen, preserve, uphold