[let up] {v.}, {informal}
1. To become less, weaker, or quiet; become slower or stop.
* /It's raining as hard as ever. It's not letting up at all./* /It snowed for three days before it let up and we could go outdoors./
2. To do less or go slower or stop; relax; stop working or working hard.
* /Grandfather has been working all his life. When is he going to let up?/* /Let up for a minute. You can't work hard all day./* /Jim ran all the way home without letting up once./
Compare: SLOW DOWN.
Contrast: BEAR DOWN.
3. To become easier, kinder, or less strict. — Usually used with "on".
* /Let up on Jane. She is sick./
Syn.: EASE UP.
4. or [change up] To pitch a ball at less than full speed in baseball. — Usually used with "on".
* /John pitched a ball that was very fast and the batter missed it. Then he let up on the next pitch and the batter was badly fooled./