Endothermic
Definition
A process that absorbs heat from its surroundings, like an instant cold pack or melting ice. The enthalpy change is positive.
Technical definition
An endothermic process absorbs heat from the surroundings at constant pressure (deltaH positive), cooling the surroundings. Examples include melting, evaporation, and cold-pack dissolution reactions.
Example
The ammonium nitrate in an instant cold pack dissolves endothermically, pulling heat from your skin and feeling cold.
Common confusion
Endothermic does not mean nonspontaneous. Ice melting above 0 C is endothermic AND spontaneous, driven by a large entropy increase.