Although wicket does refer to the three sticks (often called stumps) and the two bails that sit atop the stumps, wicket has by common use also come to mean the pitch between and including the pair of wickets at either end. It is also used to refer to a team's batsman being out as in "fall of wicket", which you'll often see in scorecards as FoW.

However, i would disagree somewhat with the technical definition of a sticky wicket as just being partly wet. It really refers to a drying wicket, the faster the wicket's drying, the stickier it usually gets. An archetypal example would be a short sharp downpour followed by sunshine on a warm day. The surface of the pitch is soft and spongy but hard underneath causing the ball to "stick", even to the point of making divots and it will deviate unpredictably both horizontally and vertically as the result of this. Getting "caught on a sticky" is something best avoided, which i suppose is what makes it an often appropriate description.

It's one of the things that make cricket such a great game, sort of being at one with the weather.