Shfuck

You say this word as a curse when you start to say the word 'shit', but mid word something happens that makes 'fuck' the more applicable of the two words so you finish your started 'sh-' with a 'fuck', thus resulting in 'shfuck'.

There's a cop behinds us, oh shfuck! He's pulling us over.

shfucking

The action of shiting while receiving or giving sex

Logan was shfucking me this morning it was delightful