noun
noninvolvement; nonintervention; neutrality
Refers to a policy or stance of not getting involved in a situation, conflict, or dispute. Often used in political, diplomatic, or personal contexts.
政府は内戦への不介入を表明した。
The government declared its nonintervention in the civil war.
彼はいつも不介入の立場をとる。
He always takes a stance of noninvolvement.
不干渉 also means 'noninterference' and is very similar; 不介入 tends to be used more in contexts of physical or military intervention, whereas 不干渉 can be used for not meddling in affairs.
Compound of 不 (non-) and 介入 (intervention). The word is a straightforward Sino-Japanese formation.