Tough Date/Hard Date

For me, it would refer to the next level of collecting difficulty after key and semi-key coins. Take the 1914S Lincoln for example, it has the 7th lowest mintage(4.2M) of the series and is valued at ~$20 in Fine so that would make it a "tough date" IMO. Conversely, a 1909VDB with a mintage of 28M should not be considered a tough date. Yes, the mintage is lower than the majority of the Lincoln series but it is certainly abundant and inexpensive in circulated and lower MS grades.

The misuse of the term is quite prevalent on ebay and amounts to nothing more than shameless hype by a seller.

I cant say for some series as I'm not familiar with them. But a lot of silver dollars were melted making them a lot less than the mintage number. This is what makes some coins a tough date, just because you see a mintage number doesn't mean that same amount still exists.

Also some coins were known to be heavily circulated. Finding them in high MS grade can also make them tough. But then again it all depends on what year and series.

Sorry for using my favorite example is the 1955-S Wheat cent a tough/hard date? It's the smallest business strike cent mintage since 1940, but that mintage figure is downright huge if compared to the 1900-1939 period.
The coin I certainly would use the term "tough/hard date" for, though, is the 1999 Russian one rouble: I'd leave the word "key" (as related to Russian 1, 2 and 5 roubles) for the 2001-2003 period with their mint-or-proof-set-only pieces, but the 1999 is just about common enough for everyone to realize it's uncommon (its significantly rarer counterpart, the 1999 two rouble - probably the rarest non-variety coin still findable in circulation - is often said to have a numismatic value of 50 roubles (probably an overblown figure - but then nobody's really saving these 1999 twos), and unlike the rouble truly deserves the term "semi-key").

There would be exceptions, where a common coin could also have that term injected into a descriptive title.
It isn't a numismatic term, but some sellers might be proper if they called a certain coin a tough date.
If you had a MS 65 1953 S nickel, that would be common, but with 5 full steps it would certainly apply.
Same goes for a deep cameo 1957 Franklin proof. A 1961 P Franklin with full bell lines in MS65 would be worth hundreds and more since they are very tough to find in that grade with FBL.
I do agree though that many auction listings abuse the term rare and tough date etc. just to get more attention.

One of the examples that came to mind was someone was describing the 2008 Lincoln Cent as a "Tough Date" - wasn't on ebay or anything, but got me thinking..

Can the term be used for varieties as well? For example... 1970S Cent- Small date - considered tough? scarce? rare? Obviously we really don't "know" what the mintage figures are for that year/mint/date style - at the same time I've heard the 1922 Plain LWC referred to as a Key Date, but we also don't have mintage figures for that either... ahh this new obsession of mine... so many questions... many more answers and very little time!

Thanks for the great responses.

My eyes are burning... but we digress

I agree with mvc, a way over used term on ebay.
I suppose it is the next tier of coins down from semikey dates and arbitrary

Just one of the many mostly misused words in Numismatics. ebay is a place where all sorts of terminology in coinage gets started. UNSERCHED is now a completely comical word in coins. I've heard many dealers at coin shows use hard to find, tuff date, difficult type, rarely available and many more such terms. Works both ways too. Once I was looking for a 20D Lincoln Cent in a high MS grade. I constantly heard dealers say, OH, that is common. You'll find one here somewhere. It took almost two years to find one. Is that a tuff date? Is is a hard to find coin? OR was I just unlucky?
Don't worry about coin terminology. If you want, start your own coin vocabulary. No rules or laws against that you know.