Definition of "pourer"

Simply screw off a bottle lid and then push the pourer into the bottle. If your bottle has a wide mouth, then you'll have to buy a wide pourer.

2010, Cheryl Charming, Just Shots: A Little Book of Liquid Fun, page 1

The visitor then passes the cup to others who are present. Each person takes a sip, handing the cup back to the pourer.

2013, Claudio Delang, Living at the Edge of Thai Society, page 104