The adj vain has 2 senses (first 2 from tagged texts)
1. (3) conceited, egotistic, egotistical, self-conceited, swollen, swollen-headed, vain -- (characteristic of false pride; having an exaggerated sense of self-importance; "a conceited fool"; "an attitude of self-conceited arrogance"; "an egotistical disregard of others"; "so swollen by victory that he was unfit for normal duty"; "growing ever more swollen-headed and arbitrary"; "vain about her clothes")
2. (2) bootless, fruitless, futile, sleeveless, vain -- (unproductive of success; "a fruitless search"; "futile years after her artistic peak"; "a sleeveless errand"; "a vain attempt")