a tall pole on a boat or ship that supports the sails 桅杆；船桅 
a tall metal tower with an aerial that sends and receives radio, television or phone signals 天线塔 people who worry about the health risks of mobile phone masts 担心手机桅杆健康风险的人
a tall pole that is used for holding a flag
Word OriginOld English mæst, of West Germanic origin; related to Dutch mast and German Mast.
Idioms
nail your colours to the mast
- (especially British English)
to say publicly and clearly what you believe or who you support 公开宣称；公开表态