Boredom

An emotion elicited based on an appraisal of stimuli as comprehensible but low on complexity. A state of relatively low arousal and dissatisfaction, which is attributed to an inadequately stimulating situation.

Reference:
Silvia, P. J. (2005). What is interesting? Exploring the appraisal structure of interest. Emotion, 5(1), 89-102. doi: 10.1037/1528-3542.5.1.89

Mikulas, W. L., & Vodanovich, S. J. (1993). The essence of boredom. The Psychological Record, 43(1), 3-12.