jackedEnglishOxford Dictionary of Englishjacked /dʒakt / (also jacked up) ▸ adjective informal mainly US English 1 physically or mentally stimulated from the effects of a drug or stimulant: a racing car driver, jacked up on amphetamines. ▪ full of nervous excitement: we're jacked about going to the semifinals. 2 (of a person) having very well-developed muscles: back in his wrestling prime, he was nicknamed the 'Anabolic Warrior' for his jacked-up physique.