The term HMM is widely used in chat rooms and doesn't imply to anything specification, nor has any specific definition for the same.
HMM usually means that this person is considering the statement that the other individual is saying, typing or asking.
It is often worn by girls. Well, this may mean that the person entirely agrees with your message and something like "yes." At times certain people use this term as a hint to tell the other individual in the chat that they are not interested in further interaction, so let's end it. If two or more messages in a row only contain "Hmm," it means that the person is least interesting and is finding the conversation as dull, sleepy, and is anxious to end to the conversation, say goodbye.
And if the other person only keeps texting "hmm," – then it might indicate that you need to stop messaging, please.
Though it is not always necessary that if someone is typing hmm, it implies that the person doesn't want to chat; it could simply be their nature. There can be a probablity that it is that person's nature or habit to write, hmm.
Maybe that individualis habitual of writing hmm while agreeing and typing, hmm after the sentence.
Of course, the mood of anyone relies on how you act. It's an important factor, therefore. These are merely options and suggestions, however, that will enable you to come to a conclusion, but it is up to you to grasp what it is. So, understanding the situation is always better than just imagining and thinking, and then finally concluding.
2.HMM- Hallmark Movies and Mysteries
HMM is the abbreviation for Hallmark Movies & Mysteries. It was previously known as Hallmark Movie Channel. Crown Media Holdings owns this digital cable and satellite television station that is situated in the United States. It has been established in the year 2004 and has its headquarters in Studio City, Los Angeles, California, United States of America. It broadcasts in English and has two sister networks, Hallmark Channel and Hallmark Drama.
Apart from these, there are several meanings and full forms of HMM. These include;
Hug me More; Hey Marry Me; Hidden Markov Model; Helicopter Marine Medium; High Molecular Mass, and so on.