A friend that has reached the level to where he/she could kiss/grope him/her with out it being considered sexual.

also as in the time to build a level and sturdy friendship, like the foundation of a well built home.
"Stewart just grabbed my butt, No biggie, he is one of my Foundation friends

Jasmin just cop'd a feel of my junk, It's all good, she is one of my Foundation friends
by Stewart D February 28, 2007
Get the foundation friend mug.