1. To judge or to evaluate someone or something incorrectly, or to form false expectations as to the consequences of an action.
2. To make a wrong judgment about what will happen or what to do in a situation.
3. To count or to estimate something incorrectly.
4. Etymology: from mis-, "bad, wrong" + calculate, "to compute, to estimate by mathematical means; from Latin calculatus, calculare, "to reckon, to compute," from calculus, "reckoning, account"; originally, "pebble used as a reckoning counter" from calx, calcis, "limestone".