If you describe something or someone as undesirable, you think they will have harmful effects.
例句
Inflation is considered to be undesirable because of its adverse effects on income distribution...通货膨胀被认为是有害的，因为它会对收入分配产生不利影响。A large group of undesirable strangers crashed her party.一大群不受欢迎的陌生人不请自来，搅了她的聚会。
N-COUNT
不受欢迎的人；不良分子；危险人物
Undesirables are people who a particular government considers to be dangerous or a threat to society, and therefore wants to get rid of.
例句
The Home Office is usually quick to deport undesirables.内政部通常会迅速地将不受欢迎人士驱逐出境。