Is it a W or an upside down M?
The W character isn't part of the Hebrew alphabet, but it is a representation of a character in the earlier Phonecian alphabet where it was the pre-cursor to the Roman F, G, U and V (as I recall).
It was added to the Roman alphabet in the middle ages, usually as a representation of the Greek Omega....
Symbolically Omega can mean the end of a path, or the end of a pattern, or the fulfillment of a quest. Lots of possibilities for the symbol on the Ace of Cups!
However, to me the letter doesn't so much look like a W as it does like an upside down M.
M is a very powerful letter! In many cultures (including the Greeks and the Romans), the M-like character represents androgyny or the inclusion or blending of both genders. Combined with the other imagery of the Ace of Cups, this opens up some pretty interesting possibilities!
Ah... but why is it upside down? I have lots of theories about that! It all depends on what the question was and where the card shows up in a reading as far as I'm concerned.
And of course, once you figure out what all that means, then you'll suddenly notice that the cup runneth over into five streams.... what could that possibly signify???
Oh... and those water lillies! What kind of message do those send?
Yup... the Ace of Cups has probably the most complex imagery of any card in the Waite-Smith deck. Lots and lots there to work with!