A piece of piss
Definition 1 of 1
Pro Tip 1/3Informal Slang
This phrase is very informal and considered slang. It's inappropriate in formal or professional settings. 
I wouldn't say completing the project was a piece of piss in front of the boss.
Pro Tip 2/3Potentially Offensive
The word 'piss' can be considered vulgar. Some people might find the phrase offensive. 
She whispered that the task was a piece of piss, aware that her grandmother might disapprove.
Pro Tip 3/3Culturally Specific
This phrase is mostly used in the UK and Australia. Other English speakers might not understand it. 
When I said it was a piece of piss, my American friend didn't get it.