A "calmette" is a person who is new or inexperienced in a subject, usually an online dating site. Calmettes are usually annoying and excessively stupid. Do not confuse calmettes with calvins, who are inexperienced people that tend to be more mature and strive to become better.
Guy: If I could rearrange the alphabet, I'd put U and I together.
Girl: Ew gtfo you calmette.