It means husband 丈夫.

While we're on the subject, an informal term that can be used for both husband and boyfriend is 老公。 Beware that it doesn't primarily mean boyfriend, but there are plenty of girls who refer to their boyfriend this way. On the other hand, 老婆, the informal term for wife, is not used for "girlfriend".

Thanks

Husband. In china, teacher is a respected job. So, the atmosphere conveyed in this satuation was positive (or formal). As a Chinese, In my book, "boyfriend" isn't as formal as "husband".