An abbreviation in pot-smoking culture for "tolerance break." It is a period of time designated to free frequent cannabis smokers of the tolerance that builds up after long periods of use. There is no certain time for a TB. For some lighter smokers a few days does the trick. For heavier smokers, sometimes a week or two is better.
"Hey Lee, you wanna come over now and smoke a few bowls out of my new 4ft bong?"
"Uhhh..not today, I'm kinda busy."
"But Lee, it's that indoor grown Purple Kush my cousin gets from the medical dispensary."
"Ok Jerry, I'm going to just say it. I'm taking a TB. And nothing is going to change that."
"Oh really? Did I mention it is crossed with Sour Diesel?"
"Fuck, pack up a bowl then. 2 days is a long enough TB for me anyways."