random                
 adjective uk/ˈræn.dəm/ us/ˈræn.dəm/
C1 任意的;随机的;胡乱的
happening, done, or chosen by chance rather than according to a plan
  random checks/tests/attacks 随机检查/随机测试/胡乱攻击 
 We asked a random sample/selection of people what they thought. 我们随机挑选一些人,问了他们的想法。 
  informal奇怪的,异常的 
strange or unusual
  I just saw Billy wearing a top hat - he's so random! 我刚才看见比利戴着一个高帽子——样子太奇怪了! 
  informal未知的 
unknown and unexpected in a particular situation
  Some random guy walked in. 有个人随便进来了。 
 at randomC1 任意地;随意地;随机地
by chance, or without being chosen intentionally
  The winning entry will be the first correct answer drawn at random. 从所有给出正确答案的参赛者中,随意抽出的第一个将获得大奖。 
 - More examples
 - And what might be the underlying significance of these supposedly random acts of violence?
 - To my untutored eye that just looks like a load of random brush strokes and yet it's a very valuable painting.
 - It seems that the attack was a random act of violence.
 - The survey was carried out among a random sample of voters.
 - The security guards carried out random checks on people entering the building.
 
random       
noun [ C ]  informal uk/ˈræn.dəm/ us/ˈræn.dəm/
 任意的某个人
an unknown or unexpected person
  You can't make a whole movie with randoms off the street. 你不能在街上随便找些人拍完一整部电影。