[ah-bee] n.
sir (but informal) / bro
DT: older brother
Although the original spelling of this word is “ağabey” the common modern pronunciation “abi” is starting to replace it in written language as well.
Turkish has no gender differentiations in grammar which makes things simple for a number of reasons, however they love to genderize everyone all the time. If you present masculine they might call you abi.