Serendipity is when someone finds something that they weren't expecting to find. The word has been voted as one of the ten English words that were hardest to translate in June 2004 by a British translation company. However, due to its sociological use, the word has been exported into many other languages. In the simplest of words, it means a "happy accident" or a "pleasant surprise".
It is true that my discovery of LSD was a chance discovery, but it was the outcome of planned experiments and these experiments took place in the framework of systematic pharmaceutical, chemical research. It could better be described as serendipity.