Check out this short post on the difference between undulant and unguent from the Libro Editing blog.
Undulant is a second adjective that originates from undulate (the more common adjective is undulating, but why have one adjective when you can have two lovely unusual ones?). So it means something that is undulating, or moving with a smooth, wave-like action.
An unguent, which is a noun, is a soft and viscous or greasy substance which is used either for lubrication or as an ointment.
So now you know.