Adjective
non-transposing (not comparable)
(music) a musical instrument that is written in a the same pitch to how it sounds.
Violin is a non-transposing instrument
The marimba is a non-transposing instrument with no octave displacement, unlike the xylophone which sounds one octave higher than written and the glockenspiel which sounds two octaves higher than written. Source: Internet
This puts the notes in exactly the same staff position as they would be if the music were written in a (non-transposing) tenor clef, although the key signature and some accidentals must be adjusted. Source: Internet