wolf tone - (noun) 

(music) A wolf tone or wolf note; an unpleasant tone produced when a note matches the natural resonating frequency of the body of a musical instrument, the quality of which may be likened to the howl of a wolf.

This cello has a terrible wolf on the D string around 'F'.

Read more at https://en.wiktionary.org/wiki/wolf_tone

[German; from the howling sound]

a (1) :dissonance in some chords on organs, pianos, or other instruments with fixed tones tuned by unequal temperament  (2) :an instance of such dissonance

b :a harshness due to faulty vibration in various tones in a bowed instrument

Read more at https://www.merriam-webster.com