0 a name or other word that you sometimes need to type in along with a password before you are allowed to use a computer or a website:
1 a name or other information that you enter, usually with a password (= a secret word, or series of letters and numbers) in order to use a computer system, website, etc.:
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.