Thinking of it...

No-strings-attached is also a commitment. You're committed to the fact that you are not committed. It's a relationship even those aren't usually referred as such and usually preferred by individuals who don't want to commit and who avoid relationships...
Answers.com defines a relationship like this:

re·la·tion·ship (rĭ-lā'shən-shĭp')
n.
1. The condition or fact of being related; connection or association.
2. Connection by blood or marriage; kinship.
3. A particular type of connection existing between people related to or having dealings with each other: has a close relationship with his siblings.
4. A romantic or sexual involvement.

Mostly 3. and 4., the point being that every connection you've to someone else is a relationship. Therefore only way to avoid relationships is to move in to a cave and never ever meet anyone.

Humans should learn to be more definitive if you ask from me.