What is the meaning of hashir?

Allah's Messenger S.A.W.S said: I have many names: I am Muhammad, I am Ahmad, I am al-Mahi (obliterater) through whom Allah obliterates unbelief, and I am Hashir (the gatherer) at whose feet people will be gathered (on Judgment Day), and I am 'Aqib (after whom there would be other prophet), and Allah has named him as compassionate and merciful.

[Sahih Muslim]