Caymus is the first cat I ever heard trill. I think I like the word, "chirrup" for it more because it the sound of that word sounds more like the sound they make than "trill" does. I actually didn't know what on Earth it was called - but sounds like a rolling of the tongue to me.
Yesterday, a Floppycats reader, Brian, pointed out that he heard Charlie trill in the video below at 3:30.
Brian went on to say, "A trill is also called a chirrup. The zoologist Desmond Morris, in his book "Catwatching" (a wonderful book by the way on cat behaviour and cat terms) says that the mother cat trills to her kittens to tell them to come to her or follow me.
Notice how Charlie moved just after trilling? Desmond Morris says adult cats will make this sound when they move off and or to a place where there is food or expect food."
Does your kitty trill or chirrup?