The Free On-line Dictionary of Computing (18 March 2015):
greatest lower bound
(glb, meet, infimum) The greatest lower bound of two
elements, a and b is an element c such that c <= a and c <= b
and if there is any other lower bound c' then c' <= c.
The greatest lower bound of a set S is the greatest element b
such that for all s in S, b <= s. The glb of mutually
comparable elements is their minimum but in the presence of
incomparable elements, if the glb exists, it will be some
other element less than all of them.
glb is the dual to least upper bound.
(In LaTeX "<=" is written as \sqsubseteq, the glb of two
elements a and b is written as a \sqcap b and the glb of set
S as \bigsqcap S).