1. (

• selenium ,
• Se ,
• atomic_number_ ,

) a toxic nonmetallic element related to sulfur and tellurium; occurs in several allotropic forms; a stable grey metallike allotrope conducts electricity better in the light than in the dark and is used in photocells; occurs in sulfide ores (as pyrite) ;

2. (

• southeast ,
• sou'-east ,
• southeastward ,
• SE

) the compass point midway between south and east; at 135 degrees ;