sturdy and strong in form, constitution, or construction
"a robust body"
"a robust perennial"
marked by richness and fullness of flavor
"a rich ruby port"
"full-bodied wines"
"a robust claret"
"the robust flavor of fresh-brewed coffee"
strong enough to withstand or overcome intellectual challenges or adversity
"the experiment yielded robust results"
"a robust faith"
Evincing strength and health; strong.
"The robust oak tree stood tall despite the fierce winter storm."
In plain English: Robust means something is strong, healthy, and able to handle difficult conditions without breaking easily.
"The server is robust enough to handle thousands of users without crashing."
The word robust entered English as a learned borrowing from the Latin rōbustus. It originally meant strong or sturdy and has retained that core meaning ever since.