To deviate from the original topic of conversation, to go off topic. Typically one says this phrase when they realized they have gone off topic and decide to return to the original point.
Another definition is to return to an original point.
Man1: Yes yes I know I'm a slacker and an asshole, but I digress. We need to come up with a plan now. (bad example sorry)
George was doing so well with getting his grades up but he's digressed into that bad behavior of drinking and partyingall night and not doing any work.
They were having a rollicking discussion when he suddenly veered off topic. This was made all the more obvious by scooting his chair over just a tish (titch, skosh, trifle) and announcing that he was now inside the Circle of Digression.
An interesting, engaging way of deviating or wandering away from the main topic or purpose when debating; departing from the principal line of argument, plot, study, etc. in order to confuse the opponent and utilise the confusion by declaring victory after the opponent confesses they do not follow. When an argument in itself is a digression and possibly nonfactual or entirely false, yet holds the attention or curiosity of the observer.
Coined by a Finnish man, who wished to remain anonymous.