Their relationship was totally asexual.

他们之间的关系根本与性无关。

...asexual reproduction.

无性繁殖

...asexual parasites.

无性器官的寄生虫

It is another unfortunate myth of our culture that older people are asexual.

我们的文化里还有一种错误观念，就是认为上了年纪的人就不再有性欲了。