hypo Share definition Flag slang, hypodermic injection. syringe, needle, or both. a small syringe used with a sterile needle for injection of material under the skin. im, iv.. "i filled the hypo up and stick it into the arm" hypo by hypo May 13, 2005 Words you can keep railfan mug chonk mug chud mug based mug 67 mug slime mug mogging mug chopped mug thot mug glazing mug huzz mug yams mug larp mug unc mug cracked mug simp mug baddie mug bop mug lolcow mug