Big Chop or 'BC' is when a person cuts their hair to obtain the 'natural' state. The person cuts out the hair dye, chemical perm, or relaxer from their hair.
Lots of women cut/chop the relaxer or perm from their hair to begin or continue the growth of their natural hair. Meaning that they've done the Big Chop.
My BC was January 1st and I've been experiencing my curls and learning new styles for short hair.