A David Foster Wallace-ism. His (thoroughly dry) definition is 'refers to a particular kind of irony where the very macabre and the very mundane combine in such a way as to reveal the former's perpetual containment within the latter'. To wit - (again, a quote from DFW) 'Ted Bundy wasn't particularly Lynchian, but good old Jeffrey Dahmer, with his victim's various anatomies neatly seperated and stored in his fridge alongside his chocolate milk and Shedd Spread, was thoroughgoingly Lynchian.'

A Lynchian conversation is one that is on the topic of a small, mundane matter, say, the various merits of Legos orver K'Nex, but a strong undercurrent of psychosis flows throughout the whole. Say, you prefer K'Nex over Legos for purely aesthetic reasons, but person two has allergic reactions to brightly colored plastic tubing and can therefore only use Lego bricks, and he/she's breaking out into hives as you speak, and he/she's becoming extremely agitated and striking out at flies which have mysteriously began to buzz about her head while speaking quicker and louder with a developing stutter about the lack of free-form originality that results from the basic structure of K'Nex in atomic form, until person two is covered in unsightly boils, screaming, and killing flies with a rash-red limb. And then it's quiet, and life goes on. That, for example, is a Lynchian conversation. Should you ever have one of these conversations, exit immediately, through any means necessary.