A mum made a 'good luck' cake for her son. She didn't notice her big NSFW mistake.

Let’s be honest, we’ve all tried our best to make a cake with a beautiful message on it.

But for most of us, that stringy icing doesn’t exactly go onto the cake as we’d like it too.

For some it might look like is says “Happj Birthray” instead of “Happy Birthday”, but for this unlucky mum, her spelling mistake was very inappropriate.

It’s a word you really shouldn’t say out loud.

You see, a friend of the unlucky mum proudly posted a photo of a birthday cake on Reddit with the caption “A friend made a cake for her son last week.”

Naturally, the people of Reddit read between the lines.

And instead of saying “Good luck @ Uni” the cake really looks like… this.

Naturally, Reddit users read between the lines.

 "What sort of person calls their son a c*nt?" wrote one.

"One who's delighted to see the little sh*t finally leave after eighteen long years," responded another.

The jokes are endless, hopefully next time this mum leaves the cake writing to... the professionals.

What hilarious cake fails have you made? Tell us in the comments!