fluid       
 noun [ C or U ] uk/ˈfluː.ɪd/ us/ˈfluː.ɪd/
C2 液体;流质
a substance that flows and is not solid
  If you have a fever you should drink plenty of fluids. 如果发烧,应多喝流质。 
 power steering fluid 助力转向液 
 The virus is contracted through exchange of bodily fluids (= liquids, such as blood, that come from the human body). 这种病毒通过体液感染。 
 - More examples
 - The patient was severely dehydrated and needed fluids urgently.
 - These tanks are used for storing fluids such as oil, petrol and kerosene.
 - Keep all your household cleaning fluids where children cannot reach them.
 - Your stomach produces a large quantity of gastric fluid.
 - There's some kind of thick fluid oozing from the trunk of the tree.
 
fluid  
adjective uk/ˈfluː.ɪd/ us/ˈfluː.ɪd/
  (MOVEMENT)      
 C2 流畅的
smooth and continuous
  fluid movements 流畅的动作 
 His piano playing was beautifully fluid, adding grace to every song he played.
   (LIKELY TO CHANGE)      
 (情况、想法或计划)不固定的,易变的
If situations, ideas, or plans are fluid, they are not fixed and are likely to change, often repeatedly and unexpectedly.
  The military situation is still very fluid. 军事局势依然很不稳定。 
 For travellers whose plans are more fluid, try looking for flights on a different day.