A penis shaped sex toy inserted into a woman's vagina for the purpose of masturbating. Originally derived from the common practice of women using large cucumbers to pleasure themselves. As in "dill" pickle or cucumber. "Doe" as in ananymous or a "john doe". Hence, dildo.
Also can mean a very dorky, nerdy, gay or annoying person.
She used her dildo every night while her husband John was out of town.
Everyone thought of Paul as a total dildo after he began reporting students who were smoking on campus.