Kerchunking is a Ham Radio term where (hopefully a legal FCC-licensed) radio operator keys their transmitter for less than a few seconds and causes a repeater to also trigger, all without saying anything.
Most of the time people kerchunk when testing their radio, especially hand-held ones, to see if it can reach the repeater from their current location. It is considered bad etiquette to do so. One should key their radio and say "testing" followed by their amateur radio call sign, then saying "(callsign) clear" after a successful test.
Example:
"Testing, KC4UWN"
"KC4UWN clear" (if you heard the repeater trigger)
Note that I used my very old callsign from back in the stone age where we used rocks and glowing bottles.