infrequent

Disturbances are relatively infrequent in British prisons.

相对来说，英国监狱不发生骚乱。

Barriers between nations are reared by slow and infrequent communication.

国与国之间隔阂是由沟通缓慢而又太少形成。

Some words are too infrequent to be worthy of inclusion in the dictionary.

一些单词使用频率太低，没有必要收入词典。