Rehk'resen was a word in the Jem'Hadar language which, when translated, meant self destruct. This word was used by any Jem'Hadar regardless of rank to destroy a Dominion base in order to prevent its capture by the enemy. The fact that the Jem'Hadar never spoke their language to outsiders ensured that their enemies were never able to use this code word against the Dominion.