The leaves will turn brown and crispy and eventually the plant will die.

...like mine did. :((

....and one of mine, Xx. Acers need to be out of cold winds and are best in pots so that you can move them to shelter if necessary. They also need acid soil not allowed to dry out. Annie

That, of course, is assuming that you meant an Acer palmatum! Many other Acers are less sensitive.

It is not necessary to keep your acer palmatum in a pot, all of ours are in the ground and grow much better this way and, generally, do not need watering. Just select a spot in your garden that is not windy and not in full sunshine. If your acer is not a palmatum has it been affected by drought?