Maxwell wrote:
Thanks Lizet.
Fascinating! I never thought of it as an acronym. Just a word birders use like Dip and stringer.
I wonder if it started like that and got corrupted here?
I shall try this out at the next opportunity. Your spelling makes sense.
I can't wait to see some diehards faces when I ask "Did you get the GISS!"

JVR. So you are saying your streaked breasted Steppe does exist? (Don't get me wrong, I agree!)
Maxwell, DD's Steppe Eagle has got a streaked breast... I'll take that one as a "first" example (for me) of a Steppe eagle with a streaked breast. I'd love to see another example or two just because..., but rest assured, I'm 100% comfortable with the ID as it stands.
Jizz is the same term used by birders to describe the overall impression or appearance of a bird based on such features as shape, posture, flying style or other habitual movements, size and colouration.
It is the general impression one gets from observing a bird and one can learn to make a reliable ID in the field at a glance. Jizz is often useful for identifying to the family rather than the species level. Once that penny drops, one can focus on those features required to make the species ID.
I found that this helped me hugely when I visited both Brazil and England; both destinations on very short notice so that I had no time to prepare. However, my feel for African birds helped a lot narrow down the probabilities.
(My first English blackbird i.e. I could describe as a thrush-like and -sized all-black bird with yellow bill and eyering... all that at a glance...)
Anyhow... the origin of the word is actually not known. There is a theory that it comes from the World War II air force acronym GISS for "General Impression of Size and Shape (of an aircraft)", but according to the Oxford English Dictionary the birding term "Jizz" was first recorded earlier than that in 1920.