1.
without looking aside; single-mindedly; with total focus; without distraction
Doing something with complete concentration, without being distracted by anything else. Literally 'without even glancing to the side.' Always used in a positive sense, praising dedication and focus.
脇目も振らず走った。
I ran without looking aside.
脇目も振らず勉強に打ち込んだ。
I devoted myself to studying single-mindedly.
彼女は脇目も振らず仕事に集中して、三年で部長に昇進した。
She focused on her work single-mindedly and was promoted to department head in three years.
脇目 means 'a sideways glance' and 振らず is the negative form of 振る (to turn). The expression is always used in the fixed negative form — you cannot say 脇目を振る. Functions as an adverb modifying the following verb. Commonly paired with: 走る (to run), 働く (to work), 勉強する (to study), 進む (to advance). Conveys admiration for intense dedication.