unobtrusively       
adverb  approving uk/ˌʌn.əbˈtruː.sɪv.li/ us/ˌʌn.əbˈtruː.sɪv.li/
 不引人注目地,不张扬地,不惹眼地
in a way that is not easy to notice
  He asked if he could unobtrusively observe the convention. 他问是否可以私下观察大会。 
 The houses blend unobtrusively into the landscape.  房屋与景观和谐地融为一体。 
 See: unobtrusive
 - More examples
 - We intend to operate as unobtrusively and efficiently as possible.
 - Radio has survived because it slips unobtrusively into your domestic routine.
 - She smiled and unobtrusively pressed a buzzer to summon a doctor.