Perhaps you need to take the Papa J's Character Inventory. Anybody can look it up in a dictionary. I'd rather describe than define a dependable person.
Dependable people follow thru on promises they make.
They don't break their word unless a genuine emergency arises. Dependable people are nice to know because they don't need follow-up phone calls in order to keep a promise or a commitment. If they say they'll do it, they'll do it. One can treat their word like money in the bank. Dependable people don't need a lot of direction or coaching in order to get the job done properly.