joist
Concise Oxford English Dictionary © 2008 Oxford University Press:
joist /dʒɔɪst/
▶noun a length of timber or steel supporting the floor or ceiling of a building.
– derivatives
joisted adjective.
joisted adjective.
– origin ME giste, from OFr., ‘beam supporting a bridge’, based on L. jacere ‘lie down’.
'joist' also found in these Oxford entries:

