To make a major mistake during an activity such as cooking, or in the creation of something like a work of art etc. The words can also be used to indicate a serious detrimental condition that has contributed to a breakdown or termination of a relationship.
Hey Baz how's your love life with Nadene? Cool?
No man she's sick of me. I got caught by her in bed with her best friend! It was a stupid drunken thing! I've made such a stupid mistake. We had such a good relationship goin' I've really buggered it up!
A tall, muscular, ugly woman
Billy take a gander at that broad.
The big un over there - looks like Desperate Dan in a skirt.
Crikey! What a steg!