The noun doubt has 2 senses (first 2 from tagged texts)
1. (26) doubt, uncertainty, incertitude, dubiety, doubtfulness, dubiousness -- (the state of being unsure of something)
2. (4) doubt, dubiousness, doubtfulness, question -- (uncertainty about the truth or factuality of existence of something; "the dubiousness of his claim"; "there is no question about the validity of the enterprise")
Overview of verb doubt
The verb doubt has 2 senses (first 2 from tagged texts)
1. (17) doubt -- (consider unlikely or have doubts about; "I doubt that she will accept his proposal of marriage")
2. (1) doubt -- (lack confidence in or have doubts about; "I doubt these reports"; "I suspect her true motives"; "she distrusts her stepmother")