What is meant by the Prophet's (PBUH) saying "they remember Allah" in the Hadith: (No people rise from an assembly in which they did not remember Allah except that they rise as if from the carcass of a donkey...)?

Any gathering in which Allah is not mentioned will be a source of regret for its participants on the Day of Resurrection. They liken it to the carcass of a donkey, and the ugliness of such a gathering intensifies if it includes backbiting, slandering, and forbidden acts.