buttress

Short definition from Wiktionary

Noun

1. 1
   A brick, concrete or stone structure built against another structure to support it.
2. 2
   Anything that serves to support something; a prop.
3. 3
   A buttress-root.
4. 4
   A feature jutting prominently out from a mountain or rock.
5. 5
   Anything that supports or strengthens.

Verb

1. 1
   To support something physically with, or as if with, a prop or buttress.
2. 2
   To support something or someone by supplying evidence.