This refers to the loss of ordinary connections between thoughts, so that language flows in a broadly logical direction, with one thought leading to another, and so on.

At its most severe the person can hardly make any sense in conversation at all, or be appearing to talk nonsense; in more subtle forms there may just be a "loosening of associations" between the thoughts expressed so that the person appears to keep 'losing the point' or 'going off on a tangient'.

This is symptom of Psychosis although Cannabis Misuse or intoxication with other drugs can cause it, too.