What is the meaning of "al-Majlis" in the noble Hadith, and does it include eating and sleeping, or passing by for a few moments, or walking on the way to the mosque?

The "gathering" (majlis) referred to in the hadith is one that is prolonged and involves much idle talk and human discourse, which may necessitate expiation. This expiation is achieved by remembering Allah and sending blessings upon His Prophet (peace be upon him). This is supported by Al-Hakim's narration of the hadith, which states: "Whichever people sit and prolong their sitting, then disperse before remembering Allah Almighty or sending blessings upon His Prophet, there will be a deficiency upon them from Allah. If He wills, He will punish them; and if He wills, He will forgive them." The accountability is lifted by any remembrance of Allah Almighty.