De minimis is a Latin expression meaning about minimal things, normally in the locutions de minimis non curat praetor ("The praetor does not concern himself with trifles") or de minimis non curat lex ("The law does not concern itself with trifles").
In risk assessment, it refers to a level of risk that is too small to be concerned with. Some refer to this as a "virtually safe" level.
Read more about De Minimis: Examples of Application of The de Minimis Rule