blocker
/ˈblɒkə(r)/noun
1- a person or thing that blocks something, in particular阻塞物; 阻拦者, 尤指：
1.1
- Cricket a habitually defensive batsman【板球】防守型击球手。
1.2
- American Football a player whose task it is to block for the ball-carrier【美橄】（协助持球队员的）阻挡队员。
1.3
- a substance which prevents or inhibits a given physiological function阻滞剂。