A more thorough explanation:

An abandoned trademark is a mark that the owner has stopped using and has no intention of using again in the future. It may also refer to a mark that has lost its distinctive significance or has become a generic term. Nonuse of a mark for three consecutive years is considered evidence of abandonment under the Lanham Act.

For example, if a company stops using its logo and has no plans to use it again, the logo becomes an abandoned trademark. The owner of an abandoned mark has no trademark rights to exclude others from using it.