mai;N ne rokaa raat ;Gaalib ko vagarnah dekhte
us ke sail-e giryah me;N garduu;N kaf-e sailaab thaa
1) I stopped Ghalib last night, otherwise [you/we] would have seen
2a) in his torrent of weeping, the sky would have been foam of the
2b) in his torrent of weeping, the sky was foam of the flood
vagarnah is simply an archaic full form of varnah ; GRAMMAR.
sail : 'A flowing; a flow of water, a torrent, a current'. (Platts p.712)
sailaab : 'Abounding with water, flooded; —s.m. A flood, torrent, stream, deluge, inundation'. (Platts p.712)