Endorsement = The action of publicly declaring one’s support
A retweet may not always equal an endorsement, but it certainly can carry a lot of weight.
Examples of endorsements
Tweets as endorsements/recommendations
1. to make public one’s negative opinion of (a politician, cause, product, etc.).
2. (of a celebrity) to agree not to be associated with (a product), usually for a fee, because their public image is considered detrimental to its sales.