A defined relationship is one where both you and the woman you're dating or hooking up with have been crystal clear with each other about your intentions, i.e as to whether the relationship is monogamous or non-monogamous, serious or casual, short-term/mid-term/long-term, etc. These things have been discussed, and everyone is clear about what the relationship is and there is absolutely no confusion.
An undefined relationship is the opposite of this, usually where a guy and girl are 'seeing each other' for a while, and have spent time together, even been sexually intimate etc, but neither party has actually discussed verbally as to what sort of relationship it actually is. The result is confusion and ambiguity on both sides.
I write this post because one of the things I've seen a lot of indirect guys do is they start seeing a girl, but never actually let her know precisely what type of relationship they're looking for. For example, if they just want casual sex or a fuck buddy, they meet a girl and start hanging out with her, sleeping with her etc, but they never actually verbally tell the girl that they were looking for a fuck buddy or no strings casual sex etc. Instead, they just sort of 'string the girl along', and try to show their intentions with their actions rather than their words by 'not acting like her boyfriend'/'not treating her like their serious girlfriend' etc in the hope that she'll somehow mysteriously and subliminally understand that you don't want anything serious with her and that everything will be fine and run smoothly.
Then what usually happens is, after a few weeks or months of seeing each other, the girl will out of the blue say something like 'So what are we?' or 'Where is this going?'. The indirect guy will simply deflect such questions with some evasive, douchebag comeback he learned on a seduction forum, mistakenly believing he's handled the situation correctly and that he'll be able to continue seeing the girl indefinitely without having to commit to her, and not run into any further questions about 'where the relationship is heading' etc (yes, the members of sosuave.net, I'm calling you lot out on being guilty of this).
The end result is always the same: the girl ends up being angry and resentful towards the guy because he wasn't verbally clear and honest at the start with her about what he wanted, the 'relationship' they had crumbles like a building with no solid foundations, and both parties end up breaking up full of bitterness and resentment for each other.
The simple way to avoid this trap: be upfront and honest with women
The point these guys miss is that it's actually easier and more effective to simply be upfront and honest with women. There is no need to play games. There is no need to 'string women along' and perpetually keep being verbally evasive about your intentions. There is no need to play the game of trying to have an undefined relationship.
When you let women know right from the start specifically what you're looking for in an open and honest manner, you won't ever get the 'Where is this going?' or 'What are we?' questions because she will already know what you're looking for and there will be no confusion and therefore no need for her to ask you these questions later on. But for some bizarre reason, many (indirect) guys miss this simple concept and seem to believe that leaving their relationship undefined will work out in their favour. The fact is, it never does.
Never operate in the 'undefined relationship' category. It never works, and will always crash and burn sooner rather than later. So always tell women specifically what you're looking for either in the first conversation with them, or at the very latest when you next meet up with them after that. You have to let women know with your WORDS as to what you're looking for....guys need to get past this bullshit idea that you can somehow communicate your intentions to women with your actions. You can't. End of.
I go over exactly how to tell women your specific romantic/sexual intentions in my second ebook, and once you get the hang of it you'll find it's very simple and liberating.