What's the meaning of "get behind"?

Question

During a discussion, people were criticizing the teen singer Justin Bieber of his poor style of dress on one of his photos wearing an outfit that included a drop crotch pants. Someone then mentioned about his roomate who wears the same style of pants, he said:

My roomie has like 4 pairs of rick owens drop crotches.

Another person replied:

That's pretty ballin but I just can't get behind the drop crotch look.

What does get behind mean? Does it mean giving support to or approval of somebody/something?

Answer 1

I wouldn't like to say for sure it's the "origin", but OP's usage strikes me as a shortened version of...

get behind the mule (and push him, to help make progress in difficult terrain)

...which itself is primarily a modern idiom (popularised by Tom Waits among others) that alludes back to...

put your shoulder to the wheel (help the mules/horses move the wagon forward, by pushing)

That's to say, the basic meaning of get behind is support, as OP surmises. But in practice people often say they can't get behind [an idea, or a proposed course of action] when what they mean is they don't accept it. And sometimes (perhaps by association with get = grasp), when they don't understand it.

Answer 2

The other answers are correct about the meaning. However, I'd like to go into some more detail about how you can distinguish this meaning from the other two.

Take a look at this definition from MacMillan. It's divided into two senses:

1. The first is getting behind on work you need to do, or getting behind with some bills you need to pay. In other words, it means you should have done more or paid more than you have by now. Since this sense is intransitive, you'll see phrases like:

   • He's getting behind with his mortgage payments.
   • She's getting behind on her homework.

   In both of these examples, the phrasal verb getting behind is followed by a preposition phrase. This is different from sense two:

2. This sense is the one explained by FumbleFingers and Flimzy, meaning to support. This sense is transitive, so it takes a direct object:

   • My parents really got behind my idea and supported me all the way.
   • Now that's a candidate I can get behind.

   Notice how in both of these examples, you're getting behind something or someone.

   There is one more interpretation, though. What if it's not the phrasal verb get behind, but the combination of the verb get and a preposition phrase beginning with behind? Let's take a look:

3. The third sense of this phrase is the literal one: to get behind someone or something physically:

   • I lit the fuse on the dynamite, ran as fast as I could, and got behind the brick wall.
   • I saw the soldiers coming, so I told my daughter to get behind me.

   This sense looks like sense 2, so you'll need to distinguish them by context. Which one makes more sense?

Note that only senses 1 and 2 are given in the dictionary entry I linked. That's because sense 3 is the literal combination of the two words, and dictionaries don't list that sort of thing. Keep that in mind when you look up a phrasal verb in the dictionary--it's usually possible to use the words that make up a phrasal verb literally.

Answer 3

Yes, in this context, to get behind means to give support or approval.

I believe the term comes from the concept of a military leader, such as when whose subordinates are behind him when he's leading them into battle.

As an example, to "get behind General Washington" would be to say you support General Washington, and by extension, his cause (an independent America).