Snipe

Snipe is a shallow extra-deep cut at the very beginning or end of a board passed through a thickness planer or jointer, leaving that few inches slightly thinner than the rest of the board. It happens because the board isn't yet (or is no longer) supported by both infeed and outfeed rollers simultaneously right at the start and end of the pass, letting the cutterhead dip slightly into the unsupported end.

It's a well-known, largely preventable machine quirk rather than a sign of a dull blade or bad technique -- supporting the board's leading and trailing ends with extra outfeed/infeed support, or simply planing boards a few inches longer than needed and trimming the sniped ends off afterward, are both standard workarounds.