1. head (of a household, etc.); leader; master
2. owner; proprietor; proprietress
3. subject (of a rumour, etc.); doer (of a deed)
そして、声の主を探す。Then I look for the person the voice belongs to.
4. guardian spirit (e.g. long-resident beast, usu. with mystical powers); long-time resident (or employee, etc.)
この山には主がいると言われている。They say this mountain has a guardian spirit.
5. husband
6. you