To get high. It seems (to me) that the word probably derives from the Spanish verb "chumar," which can refer to intoxication by everything from alcohol to hallucinogens, and which derives from "achuma," the mescaline-containing San
Pedro cactus native to the high, dry areas of South
America. Conjugation: chumo, chumas, chuma, chumamos, chumaís, chuman. "Estoy chumando duro" = "I'm tripping
hard."
A self-selected group of boys (including Barack Obama) at Punahou School who loved
basketball and good times called themselves the Choom
Gang. Choom is a verb, meaning “to smoke
marijuana.”