It was an oblique reference to his mother.

这是对他母亲的隐射。

《柯林斯英汉双解大词典》

She gave an oblique look to one side.

她向旁边斜看了一眼。

《新英汉大辞典》

This is an oblique reply to a simple question.

这是一个对简单问题拐弯抹角的回答。

youdao

I mentioned something of increasing importance only later, which is that you are free to pick another set of axes, not in the traditional x and y direction, but as an oblique direction.

后来我又讲了更重要的知识点,你可以随意选取另外一个坐标系,不再是传统的 x 和 y 方向,而是倾斜过的方向

耶鲁公开课 - 基础物理课程节选

Comprising of seven tiny layers, each 50 to 100 nanometers in height, the coating is made of silicon dioxide and titanium dioxide nanorods positioned at an oblique angle.

CNN: New nano coating boosts solar efficiency

The best answer to this question is an oblique one.

FORBES: Are Brands Zooming to Doomsday?

The comment was no more specific than that, but could be taken as an oblique reference to the fact that Giaka still has family within the reach of the Libyan authorities.

BBC: Waiting for the 'supergrass'