This study explored the definitions of sexual boredom in a large community sample of Portuguese individuals. A thematic analysis of written responses to the question “What is sexual boredom for you?” was conducted with 653 participants aged 18 to 75 (M = 33.14; SD = 9.01) of multiple genders, sexual orientations, and relationship types. Three main themes were identified: definitions of sexual boredom, predisposing and maintenance factors of sexual boredom, and managing of sexual boredom. Sexual monotony, sexual desire, and hedonic value stand out as defining features of sexual boredom. Findings suggest the need of a multidimensional measure of sexual boredom.