Pretty straightforward question:
Rain = raindrop
Snow = snowflake
Hail = hailstone
Sleet = ?
Sleet is a mixture of ice pellets, rain, and snow, so there isn’t one single drop of sleet.
I would go with “pellet”.
That is one definition of sleet, but apparently it’s a regional usage. What I would consider the main definition is ice pellets formed from frozen raindrops, so the term pellet would be appropriate. Different from freezing rain, which is liquid until it hits the ground, and hail which is amplified sleet 
(built up into large pellets/stones/boulders).
Yes, two definitions. Looks like OP is using the Dippin’ Dots definition. I always knew it as the wet snow/frozen rain definition, but granted I didn’t grow up in snow country. Wikipedia isn’t quite correct that the US is uniformly the former and the Commonwealth the latter.
This is what the meteorologists call “wintry mix” in my neck of the woods.
I would say “blob” probably. Or maybe “splat” - that’s the telltale sign on the car windscreen when rain is starting to turn to sleet/snow.
(Here in the UK, sleet means a mix of snow and rain. “Ice pellets” as per the US definition of sleet aren’t really well known as a thing here - I don’t think we very often have the right conditions for those to form.)
Local weather people seemed to suddenly start using “wintry mix” the last few years. I hate the phrase. I’m fine with Brach’s Bridge Mix or Chex Mix; wintry mix not so much.
Pellet
I would call it a freezing raindrop.
Sleet is freezing rain.
Actually, sleet isn’t frozen rain. Rain is melted sleet. When the individual lumps form, they’re solid, not liquid.
At least, for any significant storm. You can form liquid rain, but all you’ll get from it is a mist or drizzle.
Another vote for “pellet”. I remember TV weather folk using that term going back to …, well it was a long time ago. Okay?
Sleet is not freezing rain. Sleet is frozen rain, and I have seen it pile up without any liquid rain or snow mixed in with it.
Freezing rain is liquid rain that freezes on impact.
For some reason the word “sleetlet” came to my mind, probably after the word droplet. Obviously not official.
I think pellet is better.
A harbinger of ugh and/or ick.
In weather forecasting they use the abbreviation PL (for pellets) when referring to sleet.
We apparently have different definitions, as others have noted. In my dialect, sleet is wet. It may include some hard bits of ice, but if it’s not wet, it’s not sleet.
Hence, there is no single bit of sleet. It’s always an amalgam.
This may be why American forecasters are using that term “wintry mixture” which is new to me. We already have a term for it:sleet. If Americans don’t have that term, I can see why they would need to invent one for it.
(Piper, whose home town is currently dealing with -40 temps.)
I am from the Pacific Northwest part of the US. Sleet is a mix of rain and snow, or really wet snow. I’ve never heard of another definition.
Me and a friend a few years ago:
Me: I think it’s sleeting. I just got a peck.
Him: Just one peck?
Me: Yeah.
So, in my head, one sleet is a peck.
We do have the term. It’s just that quite a lot of us are using it to mean something else.
To me, sleet is ice pellets. If it’s wet, it’s not sleet, it’s rain. Under some weather conditions rain may mix with sleet; which I’ve been calling winter mix for longer, I think, than TV forecasters have. (Winter mix, for me, may also include a mix of snow with rain, of snow or sleet with freezing rain, or in general of any such combination. And then there’s what I call snain, which is when you can’t really tell whether it’s snow or rain; though I think that may be an idiosyncratic term. Well, maybe not; I just googled it and got a batch of dictionary hits, some of them even with the same meaning.)
That would be quite a few sleet pellets.
