groove  
noun [ C ] uk/ɡruːv/ us/ɡruːv/
  (NARROW SPACE)         
 沟;槽;辙;纹
a long, narrow, hollow space cut into a surface
  The window slides along a deep metal groove to open and close. 窗户沿着一条深深的金属槽滑动打开或关上。 
  medical specialized(身体表面的)沟 
a long, narrow space in the surface of a body part
  There may be nerve compression at the elbow in the ulnar groove. 在手肘处的尺神经沟处可能发生了神经压迫。 
 Idioms      
be/get in the grooveidiom  informal 性能出色;表现理想;进行得很成功
to be or start operating or performing successfully
  Alex Popov proved he was back in the groove by winning the 100 metres freestyle. 亚历克斯‧波波夫赢得了100米自由泳比赛,这证明他又回到了以前的良好竞技状态。 
 be (stuck) in a grooveidiom  感到单调乏味;墨守成规
to be bored because you are doing the same things that you have done for a long time
  We never do anything exciting any more - we seem to be stuck in a groove. 我们做的事情再也让人感觉不到有意思了——我们似乎太墨守成规了。