ball pat pack
What unusual characteristic do these three words share?
To answer, give two more words that share the same unusual property (but not your rationale, if you know it, the words you pick will make it clear we're thinking the same thing.
Thanks Nick for guessing qualm and drat, not what I was looking for, but I'm curious what the common thread you saw was, now I have my own word puzzle to work on!
PS: I've found 6 more words myself, but there must be more than that...