Does a debit signify a decrease in revenue?

Debit or debt? If debt, no. Revenues and debts are two separate entities. Revenues can be offset by debts, but doesn't mean revenues will be affected. If you are referring to debits, those reflect a decrease in credits or assets (or bank balance) and again, are no reflection on revenue.

Revenue accounts aren't part of the balance sheet and are used to denote income to the business, as well as expenses that the business incurs. The income statements are closed each month, with the total being transferred to the balance sheet. Entering a debit to an income account decreases the value of that account. Usually income accounts receive revenue, so a debit entry would be unusual.