'Welching' is the clunking of the base of a beer bottle or glass, whilst making various grunting or 'pirate-sounding' noises such as arrrrrr, or oarrrrr... etc etc. This is as opposed to 'clinking' or 'chinking' of the top of a bottle, and it perceived as far more masculine when in a group of lads who are all very drunk, and in agreement of a certain point of topic.
It is often accompanied by the raising of one's right elbow upwards, whilst making other peculiar noises, that would suggest that one has slightly lost the plot.
There was some serious welching going on last night!
When in agreement, one member calls out 'welching!' and group members proceed to welch in above said fashion.
To get the fizzy drink welch and use a funnel and funnel it down a mans penis hole and to eject it out via urinating and into another male/females nose then drunk with a straw.
Heyy john want to welch? john: sure i love welching shoot it up my nose then i will drink it out gee wiz guys we shuld have a welch party
The act of stuffing a woman's vagina full of grapes, then using your penis (or fist) to mash up the grapes. If you're feeling adventurous you can even use your foot. After the mashing, you may procede to drink the sweet grape elixir directly from the stanky vagina.