Trill is a tricky one.
I am offering an abbreviated version of what I found at dictionary.com
- A repetitive succession of rapidly alternating sounds.
- (Phonetics): A trill can be executed while singing, talking or whistling.
- (Music): An alternation of two rapid tones.
- To flow into a stream.
What all these definitions appear to have in common is that they posit an endless motion of sound or water that is repeated cyclically.
