Guided by or in accordance with the dictates of conscience; principled: a conscientious decision to speak out about injustice.
Thorough and assiduous: a conscientious worker; a conscientious effort to comply with the regulations.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.