Dictionary.com
definitions

tranny

1
[tran-ee]
noun, plural tran·nies. Slang.
  1. a vehicle's transmission.

Origin of tranny

1
First recorded in 1975–80; by shortening and alteration

tranny

2

or tran·nie

[tran-ee]
noun, plural tran·nies. Slang: Disparaging and Offensive.
  1. a contemptuous term used to refer to a transvestite, a transsexual, or a transgender person.

Origin of tranny

2
First recorded in 1960–65; by shortening and alteration
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018