Check Airman
I quite like...."request".....and...."blocked".
Couldn't care less whether its right or wrong....it works for me!
"Request".....I pay extra attention because you have pre-warned me that you're going to ask something.......I normally respond "go ahead request" so you know I'm ready.
"Blocked".....don't need your callsign or life history....a simple one word "blocked" alerts me to a possible need to repeat or clarify last transmission.....doesn't matter who said it..... I am aware that not all A/C carry blocking detection...and I don't think a lot of controllers understand either.
On a busy frequency, which is most of the time at London [Swanwick] Centre, I have found "request" and "blocked" to be ideal.