What your voice sounds like in the midst of puberty, when it's deeper than a child's, but higher-pitched than an adult's. This weird transitional phase from a few months to a year. This is typically heard during a boy's middle school years, at the age of 13. This is also the phase where your voice is the least stable, and where it cracks and breaks the most.
I had an in-between voice when I was in 7th Grade, it wasn't squeaky like it was when I was in elementary school, but not as deep as it is now.