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.
After an alternate reality version of the Dax symbiont was absorbed by the Unclean, it attempted to gather enough independent minds within the viroids in order to dominate a still functioning Jem'Hadar mouth in order to initiate the Dominion space station's self destruct. (DS9 novel: Time's Enemy)