desaparecer
/desapaɾeˈθeɾ/ · A2 · verb
to disappear, to go missing, to vanish, to be gone
des- (un) + aparecer (to appear) = to un-appear, i.e. disappear
Built exactly like English dis-appear: the prefix des- reverses aparecer (to appear). Both come from Latin apparere. If you know aparecer, you get desaparecer for free, and it conjugates the same way (desaparezco, like aparezco).