Can be an adjective or noun, sometimes even a verb depending on how silly you wish to sound.
Mostly used in a tongue and cheek manner.
Brett did the skeeziest thing I have ever seen.
Look at that skeezy person on the corner.
a combination of the two words, usually used to offend somebody, joke around with friends about, or just a politer way of saying skank, tease, etc.
michael: well she hooked up with me
mark: yeah she hooked up with me too
all: what a skeez