SLIPCAST
n. the default expression that your face automatically reverts to when idle—amused, melancholic, pissed off—which occurs when a strong emotion gets buried and forgotten in the psychological laundry of everyday life, leaving you wearing an unintentional vibe of pink or blue or gray, or in rare cases, a tie-dye of sheer madness.
*Taken from the Dictionary of Obscure Sorrows