simple past tense and past participle of sustain
"The bridge was sustained by strong cables that held its weight during the storm."
In plain English: To sustain something means to keep it going for a long time without stopping.
"The athlete sustained an injury during the match that would keep him out for weeks."
(of an electric arc) continuous
"heat transfer to the anode in free burning arcs"
Held continuously at a certain level.
"The singer held a high note that was sustained throughout the entire chorus without wavering."
In plain English: Sustained means something that continues steadily without stopping for a long time.
"The athlete gave a sustained performance throughout the entire game."