Definition from Wiktionary, the free dictionary
See also Hickey
hickey (plural hickeys)
- (US, slang) A bruise-like mark made during petting by pressing the mouth to the skin on one’s partner’s body and sucking.
- Used by some speakers to refer to an object whose name is unknown or cannot be recalled.
- (printing) A printing defect caused by foreign matter on the printing surface resulting in a ring where the ink is missing, appearing as a spot of ink surrounded by a halo.
- Local swelling in a tissue area, especially skin, often due to injury.
- A tool for making smooth, semicircular bends in conduit and pipe.
Derived terms 
referring to an object whose name is unknown or cannot be recalled
tool for making smooth, semicircular bends in conduit and pipe