means To lean or cause to lean at an angle from the vertical or horizontal — or, figuratively, to lose composure and start malfunctioning.

from From Middle English 'tilten,' meaning to topple or cause to fall, likely from an Old English root tied to unsteadiness. The jousting sense — charging at an opponent — gave us 'tilting at windmills' via Don Quixote, while the pinball sense (a machine going 'TILT' when shaken) handed the modern slang its meaning of frustrated breakdown.