To slay is to kill in a violent manner. You can also use it in a metaphorical way: “I’m going to slay that demon and face up to the supermarket on Christmas Eve”.
Slay (as a noun) is also an alternative spelling for sley, which is a tool which is used in weaving, to push the weft into place. No, I didn’t know that either, and I’m guessing that the author of the unfortunate poster wasn’t talking about Santa and his weaving activities.
A sleigh is a sledge drawn by reindeer or horses. A sledge is a vehicle set on runners which is used to travel over snow and ice, propelled by gravity downhill or pushed or pulled. Oh, and a sled is a North American term for sledge. Don’t say I don’t give you added value!
Season’s Greetings and I hope you enjoy 2013’s Troublesome Pairs and Trios!