A play used, as the name implies, to cut communications between the opposing hands usually to destroy an enemy entry needed to give his partner a ruff.
As South, you play in 4♠ after East opened 1♥ and West raised hearts. East overtakes West’s ♥K lead with the ♥A and switches to the ♣2. East’s plan is clear – to get in with the ♠A, put West in with the ♥Q and score a club ruff.
To snip communications between the opposing hands, you win the club, cross to the ♦A and throw your remaining heart on the ♦Q when East covers with his marked ♦K.