Threshold / Thrash / Thrush

The word of the day, so says my email, is Threshold.

This is one definition:

3   

a : the point at which a physiological or psychological effect begins to be produced (has a high threshold for pain) 

b : a level, point, or value above which something is true or will take place and below which it is not or will not

 

(definition and screen capture: via)

It's never been what I don't know that excites me.