活塞 is read as かっそく (kassoku) and means piston.
かっそく
kassoku
かつどう
movie (esp. during the silent movie period)
かっぱつ
lively
かつよう
conjugation
かつりょく
vitality
かっき
energy
かつじ
printed text
かっかざん
active volcano
いけうお
live fish and shellfish (kept in a tank in a restaurant)
かっせい
active
かつどうか
activist
かつろ
means of survival
かっしゃ
vivid description