Sexting was originally made public by dramatic consequences involving youths with contents that were disseminated and then used as a base for harassment. Despite a growing public and research interest, there is no consensus regarding its definition and measurements. As part of a larger qualitative study on sexting, we aimed to gather and compare opinions and perceptions of 32 youths (16-21 years) and 29 adults (11 parents and 18 teachers) on how sexting can be defined. Different constituent elements were discussed in terms of knowledge, mediums (text-only, photographs, videos, etc.), characteristics, actions (receiving, sending, disseminating, etc.) and contexts. The knowledge and the use of the term sexting was approximate for several participants. Youths used more suggestive elements in their definition and the vast majority of them defined sexting as an activity that could be positive and respectful between two consenting persons. It is necessary to develop a precise and consensual definition of sexting by separating different dimensions and by using a specific vocabulary according to youth perceptions as their main definition of sexting seems to be different from the one of most adults. Prevention messages should aim to reduce the risks by targeting the problems linked to sexting rather than prohibiting sexting per se. This exploratory study could pave the way for a clearer definition and measurement of sexting.