noun
uncontrolled mind; wild thoughts
Rare literary noun, almost exclusively found in the idiom 意馬心猿 (いばしんえん), meaning 'uncontrollable passions and wandering thoughts'. Not used in modern conversation.
「意馬心猿」は、心が乱れて落ち着かないことを表す四字熟語です。
The four-character idiom 意馬心猿 describes a state where the mind is restless and unsettled.