Thirsty describes someone who is too eager for a relationship. This can often be used interchangeably with someone who is very horny. Often, it will be used to describe someone who is eager or desperate for someone else. While it is usualy saved for a person you have strong feelings for, thirsty can also be utilized in a non-specific way for anything that you want very badly.
Felicia had been watching Diego from afar in their large office for a period of several months. She hadn’t quite worked up the courage to ask him out despite him being the type of man she had been looking for. Her friends like to tease her by saying she was too thirsty and it was a bad look to lust after him so obviously. Thirsty or not, she certainly wouldn’t mind a few drinks of Diego.