The Rice University Neologisms Database

Used like a prefix before an emotion to convey how stereotypical the situation is. Hashtag is a term that originally referred to the pound sign (#). It has been repurposed as a tag tracker on many social media websites, starting with Twitter. Hashtags are frequently used to accumulate all references about a certain thing or event in order to form a general archetype of that thing/event. (i.e. #cake would include different things pertaining to cake, and overall, it would provide the user with a general description of the meaning of cake.) It is this sense of the word that is used in this definition; the speaker uses “hashtag” to communicate a stereotypical emotion or feeling.