The BRRRR method is an approach to acquiring rental property in which the investor buys a property priced below what it will be worth once repaired, renovates it, places a tenant, refinances against the higher post-repair value to pull the invested cash back out, and repeats the process with that same cash. The acronym expands to buy, rehab, rent, refinance, repeat.
It has no issuing body and is not a lending product; it is a name for a sequence. The term comes out of the retail real-estate-investing world and was popularized by David Greene's 2019 book Buy, Rehab, Rent, Refinance, Repeat, published by BiggerPockets, a real-estate-investing company. Nothing about the strategy is defined by regulation, and the refinance at step four is an ordinary cash-out refinance rather than a product built for this purpose. That refinance is where the written rules are, and it is what decides whether the sequence works.
The line against the adjacent strategy is worth drawing because the first three steps look identical. House flipping sells the property after the repairs; BRRRR holds it and rents it. That difference changes the tax question, the financing, the time horizon and the risk, so the two are best treated as separate strategies that happen to share an opening.