The unheated form of tetrahydrocannabinol (Δ9-THC) that is produced in cannabis flower. See “acid cannabinoids.”
Summary from Wikipedia:
Tetrahydrocannabinolic acid (THCA, 2-COOH-THC; conjugate base tetrahydrocannabinolate) is a precursor of tetrahydrocannabinol (THC), an active component of cannabis.
THCA is found in variable quantities in fresh, undried cannabis, but is progressively decarboxylated to THC with drying, and especially under intense heating such as when cannabis is smoked or cooked into cannabis edibles. THCA is often the majority constituent in cannabis resin concentrates, such as hashish and hash oil, when prepared from high-THC cannabis plant material, frequently comprising between 50% and 90% by weight.Read more