barrel roof

基本解释

A protrusion (56) forming a ridge is disposed on one of the roof of the barrel and the plunger head.
形成脊的突起（56）设在注射筒顶部和柱塞头中的一个上。
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A distal end of the barrel defines a roof , and an elongate tip, in fluid communication with the barrel, extends from the roof .
注射筒的远端限定出顶部和从顶部延伸并与注射筒流体连通的细长尖端。
ip.com
NATO will not attack Syria militarily because Iran and Syria has a Defense Pact. Price of a Barrel of Mideastern Crude will shoot through the roof.
北约不会轰炸叙利亚的，因为叙利亚和伊朗之间有军事合作协约，不过此事会造成中东石油的价格涨到屋顶。
blog.sina.com.cn

His new network, RipeTV, offers only short shows packed with cheap thrills--3- to 15-minute snippets of dirt bike racing, lingerie models and guys barrel-rolling off a two-story roof.
FORBES: Attention Deficit Television