母線 is read as ぼせん (bosen) and means bus.
ぼせん
bosen
ぼにゅう
mother's milk
ぼけん
prefecture of birth
ぼしゅうだん
population
ぼせいこうか
maternal effect
ぼいんさんかくけい
vowel triangle
ぼいんせつぞく
hiatus
ぼへいきん
population mean
ぼけい
matrix (printing)
ぼざい
base material (in construction, etc.)
ぼいん
thumbprint
ぼがん
base rock
ぼせい
homeworld