winterizing is a process where in most cases you use a secondary solvent, like ethanol, and then drop the temp significantly and let the fats fall out of the solution. It’s then filtered and you’re left with a more pure extract to distill.
One tip if you’re unsure of some slang terms and want to find a definition, try doing a google search with the term and BHO at the end (like “winterizing BHO”)… You’ll likely find some information to get you in the right direction when you have no clue on where to start looking, or just come in here and ask us and we’ll point you in the right direction.
There’s a lot of good info in this forum on it too if you want to do some more reading on it