If there is no object to the sentence - for example 'I have washed the car' or 'I have washed the dishes' - the speaker is referring to himself or herself.
If you say 'I have washed' it probably means that you have washed your face and hands, and/or you have had a bath or shower.
NB Don't forget to use capital letters and punctuation when you are writing. Your question should have been written like this:
'I have washed'. What does it mean?
These are an important and necessary part of written language - capital letters and punctuation are not optional extras.