unobtrusive

adj.

不突出的，不引人注目的；谦虚的；不唐突的；不冒昧的

1. She's a quiet unobtrusive student.
   她是个文静而不引人注目的学生。
2. She saw only that he was quiet and unobtrusive, and she liked him for it.
   她只知道他沉静而谦逊，并因此而喜欢上他。

Unobtrusive rule-based computer usage enhancement system
Unobtrusive Sensing and Wearable Devices for Health Informatics
Unobtrusive measures: Nonreactive research in the social sciences.
GestureWrist and GesturePad: unobtrusive wearable interaction devices
Unobtrusive measures; nonreactive research in the social sciences [by] Eugene J. Webb [and others]
Recent unobtrusive studies of Black and White discrimination and prejudice: A literature review.
A wearable sensor for unobtrusive, long-term assessment of electrodermal activity.
Variability in automatic activation as an unobtrusive measure of racial attitudes: a bona fide pipeline?
Sensing from the basement:a feasibility study of unobtrusive and low-cost home activity recognition
Are Dietary Restraint Scales Valid Measures of Acute Dietary Restriction? Unobtrusive Observational Data Suggest Not.