underpart

1.The underpart of the plane's fuselage scraped the treetops.

飞机机身过树顶。

2.I don't think that the underpart barring is useful in the field.

个人认为体下横斑对野外辨识没什麽用。

3.The underparts were orangey-brown, paling towards the lower belly.

橙棕色，往下渐渐变淡。