Glossary of Terms:
 
phone plug
A 1/4-inch socket commonly used on electronic musical instruments and professional audio equipment; A mono 1/4-inch phone jack uses two conductors (tip/sleeve), and a stereo 1/4-inch phone plug uses three conductors (tip/ring/sleeve).
Source: Yamaha

Also refered as:
  1/4-inch plug
Related terms:
  1/4-inch jack   1/8-inch jack   1/8-inch plug   TRS   TS   XLR connector   balanced   headphones   input   mono jack   mono plug   output   phone jack   stereo jack   stereo plug   unbalanced