You could validly use 'contraptive' or 'contraptative' as adjectives, and at a push, nouns too. I'm assuming you don't mean the object that is a 'contraption'. I'm assuming you mean the state of being contraption-minded. I wouldn't say you'd be incorrect to use any such words, although a narrowminded examiner might. Just because the dictionary doesn't define it, doesn't mean it's not valid English. The language existed before the dictionary, and the language evolves ahead of the dictionary. The language is also too big for the dictionary to fully contain, considering its boundless ability to create new nouns and then develop adjectives from nouns etc. Why do people tend not to use such words? Because other words and word-combinations are more popular, and people tend to follow tradition when it comes to speaking a language. Consider these terms: * Inventive * Crafty * Technologically crafty * Tech-savvy * MacGyverish * Contraption-minded * Resourceful * Creatively resourceful There are endless ways to combine simple words to create precise meanings. So it just depends what you want to emphasise. The more detail you need, the more words you use.