<p>The term ‘weasel word’ is used for vague, ambiguous, or misleading language when the speaker creates an impression of meaning or certainty without committing to specific facts. In academic writings, clear presentation of the declarant’s thoughts is inevitable for the transmission and/or sharing of knowledge with high fidelity; hence, weasel words and phrases should be avoided. So far, the topic has received little attention in the behavioural sciences, including ethology, although research in fields focusing on behaviour and the mind provide fertile ground where such rhetorical strategies may go unnoticed. By presenting examples of weasel words used in ethology, we aim to demonstrate how they can lead to misunderstandings among scientists, as well as to prolonged and unproductive debates. We argue that the use of weasel words may stem equally from ingrained bad habits, knowledge gaps, anthropomorphism and inconsistent jargon. Instead of referring to mental states, the description of the behaviours should be in focus from a functional point of view. This allows more precise behaviour measurement and greater agreement in the use of terminology. Adopting a more descriptive and precise terminology may facilitate interdisciplinary discussions and lay the groundwork for novel approaches, such as synthetic or computational ethology.</p>