Congeal means to jell — to solidify or become gelatinous. Sounds gross? But wiggly Jell-O is actually congealed liquid, so it can't be that bad, right?
This word comes to us from the Old French word congeler, which means "to freeze." So when something congeals it goes from liquid to solid form, almost like freezing. No one usually likes congealed anything — whether it's chunkified old soup in the fridge or dried blood on a wound. See? Pretty gross. Jell-O is about as good as congealed gets!