[Christ]

Originally Posted by dcb

depends how you project it into 3d, could be (not a comprehensive list):

a. two tubes next to each other, I think the true name is "really cool straw from fast food restaurant"

b. two balls touching, correctly termed dognuts

c. something that looks like two hyper dimensional do-nuts

d. a torus with R = r

Actually, there are two names for the symbol ∞.

One, which is not the one I'm looking for, is Lemniscate, which represents the symbol in typeset.

Once transferred into 3d space, the symbol can be viewed as a surface with only one side and one boundary.

(That's a hint.)