Definition

• noun: a small animal that has thick, brown fur and a wide, flat tail, that cuts down trees with its teeth, and that builds dams and underwater houses with mud and branches
• noun: either of two large semiaquatic herbivorous rodents comprising a family (Castoridae including 'Castor canadensis' of North America and 'C. fiber' of Eurasia), having webbed hind feet and a broad flat scaly tail, and constructing dams and partially submerged lodges
• verb: to work energetically
• often used before another noun
• synonyms: vandyke, viso, activist