Perception Institute: Explicit bias refers to the attitudes and beliefs one has about a person or group on a conscious level. Much of the time, these biases and their expression arise as the direct result of a perceived threat. When people feel threatened, they are more likely to draw boundaries to distinguish themselves from others.
Dictionary.com: Explicit bias refers to the attitudes and beliefs you have about a person or group on a conscious level. They can be stated through language, be positive or negative, and may be exhibited through actions and behaviors.
Kirwan Institute Ohio State University: Explicit bias refers to a bias that a person knows about but that he or she may choose to conceal for purposes of social and/or political correctness. They can be identified through introspection.
My brain’s opinion is that explicit biases may be identified through what a person thinks, feels, and says at a conscious level and the behaviors or actions he or she knowingly chooses to exhibit.