This new job ability "Sacrifice" when used by a Summoner, cause a loss of given abilities(such as ATT, DEF, ACC, TP gain, etc) by a certain percentage and gives this to the summoner pet. Basically, weaken a players melee ability while strengthening a pets. I guess, you can call it a "summoner's stance".
This could add to the versatility of the job somewhat and play style. Most Summoners, tend to hold back anyway, whether from fear of AOE's or other reasons.