Quark imitates the Cardassian neck trick
The Cardassian neck trick was a Cardassian stunt that was considered amazing to behold.
When Odo was under the supervision of Doctor Mora Pol at the Bajoran Center for Science, the Cardassian High Command came to view Odo's performance of the neck trick in 2363. In Dukat's words, it "brought the house down"; Gul Hadar in particular could not stop talking about it. By the time Odo met Quark in 2365, the Ferengi had heard all about the neck trick, which Odo claimed he no longer performed. Quark thought the trick would go over well in his bar, but Odo was not interested. (DS9: "Necessary Evil")
In 2371, Odo's Cardassian informant asked him if he still performed the Cardassian neck trick. Odo sternly said he didn't, much to the informant's disappointment, as he was "so good at it". (DS9: "Improbable Cause")
The specifics of what the "neck trick" is have not been discussed, but it is presumably related to Cardassians' high necklines. From Quark's imitation, it may involve Odo imitating Cardassian physique in some way.