The phrase "slow drip" means a gradual or slow process, usually involving a small and steady flow of something, like water or information. Full definition
The launch lineup and slow drip of indie titles on the Switch will have to carry you over until this support is released. (dailydot.com)
Right now the bolt is holding in place alright with a very slow drip, but with the next oil change I will need to make a repair. (mechanics.stackexchange.com)
Since then though, there has been a steady but slow drip feed of new titles added to the roster - with plenty of notable triple - A absentees. (pocket-lint.com)