Culinary definition of fold: To incorporate a mixture (ie: meringue) by gently turning it over and over, without crushing, mashing or beating. Also, to fold dough, wraps, or sliced meat to enclose fillings.
C@H FOOD FOR THOUGHT
Folding-in well (former, above) takes practice. We have found that it never really looks like you are finished, and that's OK.
When in doubt (and this could happen often), quit folding-in before it looks like you are 100% done - otherwise you will overdo it and you'll really be done.
Always use a clean dry glass or stainless steel bowl, and always fold-in using a thin rubber or silicone spatula or a thin metal spoon.
Never use a clunky wooden spoon as that would simply 'bash out' the air - defeating and deflating your purpose.