While there is no official definition of open science, a 2015 report from the Organisation for Economic Co-operation and Development (OECD) refers to it as follows:
"...efforts by researchers, governments, research funding agencies or the scientific community itself to make the primary outputs of publicly funded research results - publications and the research data - publicly accessible in digital format with no or minimal restrictions as a means for accelerating research; these efforts are in the interest of enhancing transparency and collaboration, and fostering innovation."1
The idea is that greater accessibility of research materials, better interoperability of scientific instruments and outputs, greater collaboration between researchers, etc. will lead to an improved research landscape that is more transparent, efficient, effective, and engaging.
1. OECD (2015), "Making Open Science a Reality", OECD Science, Technology and Industry Policy Papers, No. 25, OECD Publishing, Paris. http://dx.doi.org/10.1787/5jrs2f963zs1-en. p. 7