不满 bùmǎn dissatisfied

dissatisfied; discontented; resentful; (before a number) to be less than

How to remember 不满: 不 not + 满 full = dissatisfied.

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不满 (bùmǎn) means dissatisfied or resentful, usually as a predicate or noun: 大家对这个决定很不满 (dàjiā duì zhège juédìng hěn bùmǎn) - everyone is unhappy about this decision.
It's stronger and more formal than 不高兴 (bù gāoxìng, simply unhappy); 不满 implies grievance or disapproval, often used with 对…不满 (dissatisfied with).
A separate, formal usage appears before numbers meaning 'less than/under': 不满十八岁 (bùmǎn shíbā suì) - under 18 years old - common in legal or age-restriction contexts.
As a noun it takes 表示: 表示不满 (biǎoshì bùmǎn) - to express dissatisfaction.

他对结果不满意。 Tā duì jiéguǒ bù mǎnyì.He is unsatisfied with the result.
你并不满意，对吧？ Nǐ bìng bù mǎnyì, duì ba?You're not satisfied, are you?
尽管他很富有，他还是不满足。 Jǐnguǎn tā hěn fùyǒu, tā háishì bù mǎnzú.Despite his riches, he's not contented.