Seriously (used to add emphasis), or also to express cynicism or incredulity ('you cannot be serious').
Late 20th Century revival, predominantly in Munster (Ireland), of a term first believed to be in use during the inter-war period in Britain. Neither the origin nor the reason for the revival are clear, but it is thought that there are some examples in the literature of Wodehouse & Waugh.
"Sean was goin' on about us all goin' to the gym before the pub, but we just looked at him, like, Seriously Aubrey, like."
"We tore into them pints last night, lad - I mean, Seriously Aubrey..."