A NaNoWriMo term that means that you 'fly by the seat of your pants' when you are writing your novel. You have nothing but the absolute basics planned out for your novel.
This outlook towards writing is often opposed by the 'planner', who knows exactly what is going to happen, when it will happen, and where it will happen. There is often enmity between the two types of writers.
Another pantser?! Seriously, GTFO