Show of incredulity. Short for ни фига себе, it can sometimes be written фигасе.
Фигассе… с утра полезла на свой любимый ресурс, а там хуяк-хуяк, а не ресурс.
Blimey… this morning I logged onto my favourite site, and there was bugger all, not a site.
(tokyo-number-13 @ ЖЖ, 03/2009)
