Life rarely treats us to beginnings or endings. Most of the time, we come upon something that has already started, and we leave those somethings--often--before they truly 'end.' If you described such a moment, you don't have to describe the supposed beginning or the end; you could just describe the moment as it's happening--in the middle of it's occurrence.
In 20 lines or less...
1. Capture a moment that you entered 'in the middle' of it happening. You cannot have 'a beginning' or 'ending' to the scene or moment you are describing. Just walk the reader into the scene, into the 'now.'
2. No eroticism or excessive profanity (limited expletives are OK if they clearly contribute).
3. No pre-writes.
That's it. Have fun. The poem that best captures a moment as it is happening, without regard for a clearly defined beginning or ending, will win the gold and a solid 1k in points.
If you have questions, just send me a message. Happy to be more clear if the directions are too vague.