1. joist - Noun
2. joist - Verb
A piece of timber laid horizontally, or nearly so, to which the planks of the floor, or the laths or furring strips of a ceiling, are nailed; -- called, according to its position or use, binding joist, bridging joist, ceiling joist, trimming joist, etc. See Illust. of Double-framed floor, under Double, a.
To fit or furnish with joists.
Source: Webster's dictionaryAdd a two-by-four joist hanger to the exact center of your ledger board. Source: Internet
The bomb blew down his house, and a joist pinned him by the legs, in full view of the Jesuit mission house across the way and of the people hurrying along the street. Source: Internet
Or you need to install a true junction box for a wired light and make sure it is attached to a ceiling joist or use a ceiling fan brace kit. Source: Internet
The junction box will have holes inside to allow you to screw it onto a joist, rafter, or other sturdy wood section of your house. Source: Internet