This is the 4718th most frequent German word.
waschen
"Waschen" means "to wash."
The verb 'waschen' is used in the present tense to express an action performed by the speaker themselves (reflexive usage in context with 'meine Hände').
Ich wasche meine Hände vor dem Essen.
I wash my hands before eating.
'Waschen' is used in the passive voice to indicate the need for the action of washing to be performed on the object 'Windows'.
Die Fenster müssen wieder gewaschen werden.
The windows need to be washed again.
Here, 'waschen' shows the action performed by a third party (the child) on an object (its face) directly.