descuidar
/deskwiˈdaɾ/ · B2 · verb
to neglect
😴 des- (undo) + cuidar (care) = undo the caring, so you neglect
Cuidar means to take care of; the prefix des- reverses it. Descuidar is to stop caring for something, so it gets neglected. Same root as English cuidado, careful: cuidado is care, descuidado is careless.