(idiomatic) say under one's breath, speak in a low voice

even if one says

to hold back; to suppress; to contain

anger

anger

(often informal) murder

to kill, to put to death / to ruin, to spoil / to suppress, to stifle

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

voice; chirping, singing; sound; voiced sound /

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend