A negated relation symbol indicating "not less than or equal to" in inequalities and order theory.
Examples
Basic inequality statement showing a number is not less than or equal to another
7 \nleq 5
Comparing function values at a point
f(x_0) \nleq M \text{ for some } x_0 \in [a,b]
Statement about sequence bounds
\exists n_0 \in \mathbb{N} : a_n \nleq L \text{ for all } n \geq n_0