I worked as a professional editor in trad pub for a small press. As far as the trad side of things, Midlist author means any author who is not a debut author that is not a household name but who still breaks even (on our end as the publisher, not required for them to sell out advances) at least 3/4 of their titles. -- The term comes from our backlist and frontlist, you're in the middle of that list. If you are debut you're at the bottom, if you're a household name you're at the top.
Note: I'm not 100% how you'd define it in Indie authors as you're in control of your own list and instead of up against others at the publisher, you're only against the mainstream sales.
I worked as a professional editor in trad pub for a small press. As far as the trad side of things, Midlist author means any author who is not a debut author that is not a household name but who still breaks even (on our end as the publisher, not required for them to sell out advances) at least 3/4 of their titles. -- The term comes from our backlist and frontlist, you're in the middle of that list. If you are debut you're at the bottom, if you're a household name you're at the top.
Note: I'm not 100% how you'd define it in Indie authors as you're in control of your own list and instead of up against others at the publisher, you're only against the mainstream sales.