※ Inside of dictionaries: interesting :
■ 2 [HUMOROUS] strange or different: ex) That's an interesting looking hat you're wearing, Neil!
5. Being peculiar, strange, odd, eccentric or queer.
7. Being rare or unusual.
CF. In hacker parlance, this word has strong connotations of `annoying', or `difficult', or both. Hackers relish a challenge, and enjoy wringing all the irony possible out of the ancient Chinese curse "May you live in interesting times". Oppose trivial, uninteresting.
... Websters online
※ Outside of dictionaries:
■ (...) The word “interesting” is often used to mean the opposite: when people say it in a trailing-off tone, their attention clearly wandering, you know you’ve been boring your audience witless.
■ (...) he divides the dishes into six grades: ORDINARY, STANDARD, CONNOISSEUR, INTERESTING, UNUSUAL, and EXQUISITE. (...) When using the word “interesting” in regard to cooking, we probably think “strange”. The Tofu Hyakuchin introduced nineteen recipes in this section, which described interesting dishes as being quite different dishes that would catch people by surprise.
(...) The more modern and "sympathetic" names for human feelings, derived from introspection and self-analysis, only begin to appear in large numbers about the middle of the 17th century. Loneliness, indeed, and disgust and lassitude are a little earlier; but at this time words like aversion, day-dream, dissatisfaction, discomposure, make their appearance; depression is transferred from material objects to a state of mind, and the old word reverie, which had first meant "joy" ant then "anger," acquires its modern and introspective meaning. This vocabulary of moods and feelings was increased in the 18th century by ennui, chagrin, homesickness, diffidence, apathy, while the older words, excitement, agitation, constraint, embarrassment, disappointment come to be applied to inner experiences. With these words we find a curious class of verbs and adjectives which describe not so much the objective qualities and activities of things as the effects they produce on us, our own feelings and sensations. To divert, to enliven, to entertain, to amuse, to entrance, to fascinate, to disgust, to dissatisfy, with the adjectives entertaining, exhilarating, perplexing, refreshing, and many others, are all modern words, or old words given a new and modern meaning. Some of them, indeed, are very recent, and our use of the common adjectives amusing and exciting is not found before the 19th century.Perhaps the most characteristic of all these modern adjectives is the word interesting, which is put to so many uses that we can hardly imagine how life or conversation could be carried on without it. And yet interesting is not found before 18th century, when it first meant "important", and its first use with its present meaning appears characteristically enough, in Stern's Sentimental Journey, published in 1768. About the same time the verb to bore appeared; and we who are so often bored, or interested, must, if we wish to enter into the state of mind of past ages, try to imagine a time when people thought more of objects than of their own emotions, and when, if they were bored or interested, would not name their feeling, but mention the quality or object that produced it. This change is a subtle and yet an important one; it is due to our increased self-consciousness, and our greater sense of the importance of the inner world of feeling. (...)