It says "as opposed to subject" so I'd only assume it's referring to an object as in grammar structure.
It's actually more like (3). It's the opposite of 主観. You can confirm this with its derivatives, 客観的, 客観性, etc.
Here's a Japanese dictionary entry if you want some extra info: http://dictionary.goo.ne.jp/leaf/jn2/54335/m0u/%E5%AE%A2%E8%A6%B3/
Wow, this really isn't a great definition. As Zengor said, it means "objective" as in "looking at something objectively", rather than "subjectively". "Object" in the grammar sense is 目的語 and "subject" is 主語. I've suggested some changes to JMdict to try and clear this up a bit.
Thank you for your responses. Very helpful.
"Object" as in... what?
I'm not understanding what kind of "object" this meaning refers to. "Object" as in... (1) grammar structure, ie. Subject Verb Object, or, (2) inanimate thing, or, (3) thinking of a thing objectively, which that in of itself I don't really grasp well.