Y-jack

From its shape, like a capital Y.

Y-jack (plural Y-jacks)

1. A splitter; a device used to split a single jack into two.
   • 2006, Edward C. Baig, Macs For Dummies (9th ed.), page 137:

     The answer is a small, inexpensive, plastic doodad called a splitter (or Y-jack), which as its name suggests splits a single phone jack into two. So now you can plug your computer and phone into the same wall jack

   • 2007, Rick Steves & Pat O'Connor, Rick Steves' Ireland 2008, page 14:

     If you bring along your own pair of headphones and a Y-jack, two people can share one audioguide and save.

• Y-splitter

• Jacky, jacky