unseize Share definition Flag Verb. Meaning to free something that is seized. If something is seized, for example, an engine, you must unseize it in order for it to work again. Just ask any mechanic what unseize means and they will tell you. Stupid Webster. unseize by akblack December 30, 2008 0 0 Get merch Get the unseize mug. Buy Now — $32.95 See more merch