"Slow clap" refers to a sarcastic or ironic applause given by a group of people, where each clap is done slowly and deliberately. It is typically used to mock or express disapproval towards something or someone. Full definition
Where a ray of light shines down to the bottom of the pit, and with slow claps, group hugs and tearful hallelujahs, we find redemption. (relevantmagazine.com)
Really, Deb [insert slow clap here] next time your husband suggest you do nothing but sleep, socialize and relax for a week, perhaps you might just not argue. (smittenkitchen.com)
(Insert slow claps here) Just meandering around town I averaged 17 to 19 mpg. (topspeed.com)