definitions
Encode (or Compress)
To convert for storage or transmission, particularly when the new file uses a lower data rate than the original, or a more lossy codec.
Re-encode
The process of saving a file back to its existing format after performing some kind of editing process.
Transcode
To convert to a different format of similar or like quality to gain compatibility with another program or application
Transrate
To convert to a different data rate using the same format.
Transsize
Convert to a different resolution using the same format.
Transmux
Convert to a different container format without changing the file contents.