An Odd Expression?

It's rare I hear "new" slang, even rarer when I don't realise what it means, normally the context leaves me in no doubt, this one caught me off guard;
There were two girls in the car, one seeking a male perspective.... as sometimes happens in the cab.
Seemingly there was a Canadian lad on a placement in their company whose tenure was coming to an end and he was about to head home.
The other girl (the one not talking) fancied this lad and had tried all her flirting tricks to no avail.
I was first made agree that she was indeed a very attractive girl that any red blooded male would fancy and then asked;
"If I was single and in the situation the Canadian lad was in and this girl "threw the gob on me " would I "throw the gob" back?"
HUH?
I assumed it meant kiss and answered accordingly......... but I'm not too sure?
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