Wow and flutter
Pitch wobble caused by tape or a record not moving at a perfectly steady speed.
Wow is the slow kind, a few cycles per second, typically from a record with an off-centre hole or a cassette with uneven friction. Flutter is faster and comes from the capstan, the pinch roller or motor irregularities. It's measured with a test tone around 3 kHz and quoted as a percentage, weighted for how the ear perceives the wobble. A good cassette deck managed less than a tenth of a percent.
Digital audio made the problem history; its closest relative is clock jitter, several orders of magnitude smaller and therefore handled with word clock rather than mechanics. Fittingly, wow and flutter are now sold as plugins, for anyone who wants to sound like a worn reel-to-reel.