na-adjective
narrow-minded; small-minded; petty
Derived from the Buddhist term 小乗 (Hinayana), used figuratively to describe a person or attitude that is self-centered, ungenerous, or lacking in broad-mindedness.
彼の小乗的な考え方にはうんざりする。
I'm fed up with his narrow-minded way of thinking.
小
You should change your petty attitude.
小乗 is the original Buddhist term for Hinayana; 小乗的 is the adjectival form used in a figurative, non-religious sense.
From 小乗 (Hinayana, a term in Buddhism) + 的 (adjectival suffix). The figurative meaning of 'narrow-minded' comes from the perception of Hinayana as a more self-focused path compared to Mahayana Buddhism.