1)
Third gear is another way of saying
mackin', or pimpin'. like- 3rd gear in a mac truck.
2) Third gear is that stage when a male and female are inbetween being just friends and "officially" dating
3) It may be used to describe
overdone affection between a dating couple
4) It may be used as a synonym for girlfriend or boyfriend.
Noun--
1)Hey, are you in
third gear with
Lindsey?
2) Greg, where is your third gear?
Verb--
Wow! Matt and Jamie are really third
gearing it.