The definition of honor varied widely between cultures, as did the importance placed upon it. Honor was normally synonymous with dignity and referred to the upholding of one's values. The Klingons were notorious for the emphasis they place on honor.
This may have been a more abstract way of viewing honor. But, as notions of honor were often very subjective, putting emphasis on clear objects (i.e. victory) made the Klingon able to deduce the honorable conduct (i.e. meanings used to achieve victory).
Honor was one of the most important components of Klingon philosophy. However, it was significantly different from most other cultures' definition of the word. For example, Worf once said that "Nothing is more honorable than victory". From that point of view, stabbing an adversary in the back or using a cloaked ship could be seen as honorable if this was a way of achieving victory. (DS9: "Rules of Engagement")
The notion of honor seemed to be highly relative and open to debate. Each and every Klingon could possibly have his own interpretation of what consisted of an honorable means to achieve an end. Even more, some decisions were paradoxical because two different view of honor were in contradiction. For instance, Worf indicated that it was necessary to challenge Gowron's leadership (for he's presumably acting in a dishonorable way) while General Martok was convinced that it was dishonorable to challenge the leader of the Empire in the middle of a war. (DS9: "Tacking Into the Wind")
Hence, dishonor is sometimes a concept which compels Klingons to action.
Also, another important component of Klingon honor seemed to be simplicity. For example, it was seen as more honorable to destroy a ship than to conquer a planet, to kill an adversary with a bat'leth than with a disruptor, etc.
In that sense, it was also more honorable to be defeated in hand to hand combat than be discovered plotting with Romulans.
It is to be noted, however, that achieving victory by economic means (as done by Quark) is still seen as honorable, yet many Klingons were reluctant to partake in such actions. (DS9: "The House of Quark")
This, however, does not address the difference between 'honor' and 'honorable'. Honor is a code of conduct of an individual Klingon, and honorable is the action that can be taken to achieve the honor that accrues to the individual; so each action and achievement is based upon the individual.