When singing (especially when singing in an octave already lower than one should), to try to hit a note beneath one's voice range and to produce a grinding, dissonant break in the melody before resuming the song once one can hit the notes again. Example: Danny hits ground a lot when he sings at the meetings.
HIT GROUND
Meaning of HIT GROUND in English
Slang English vocab. Английский сленговый словарь. 2012