The term "bigronil" does not have a clear definition or direct translation in English. It appears to be a combination of words, potentially from different languages or created for humorous effect. Since it is not a standard porn video tag, the description for this particular tag would be open to interpretation and personal understanding.
However, if we break down the word into its components: "big" implies a large size, while "-ronil" could potentially be derived from the Spanish or Italian word "ronco," which means "thin." In that context, it might refer to a large, thin penis. But again, this is speculation and may not accurately represent the intended meaning of the term "bigronil."