Some online dictionaries prohibit such copying of their content. Some examples below (not meant to be an exhaustive list, and any bolding for emphasis is mine) :
First, from the Stack Exchange terms of service:
"...any and all content...that you provide to the public Network ...is perpetually and irrevocably licensed to Stack Overflow on a worldwide, royalty-free, non-exclusive basis pursuant to Creative Commons licensing terms (CC BY-SA 4.0), and you grant Stack Overflow the perpetual and irrevocable right and license to access, use, process, copy, distribute, export, display and to commercially exploit such Subscriber Content, even if such Subscriber Content has been contributed and subsequently removed by you..."
Your use of the Site and its contents grants no rights to You in relation to Our intellectual property rights including, without limitation, trade marks, logos, graphics, photographs, animations, videos and text or the intellectual property of third parties in the Site and its contents. None of the Content or User Content may be downloaded, copied, reproduced, republished, edited, posted, transmitted, stored, commercially exploited, sold or distributed without the prior written permission of the copyright holder. Subject to the above You may download insubstantial extracts from the Site on any single computer for personal, non-commercial home use only, provided that no more than one copy of any information is made and all copyright and proprietary notices are kept intact.
you may "reproduce... content...only for your personal, non-commercial use. If you are a teacher, scholar or student, you may copy reasonable portions of the content...for lesson plans, interactive whiteboards, reports, dissertations, presentations, school newspapers and for similar nonprofit educational purposes to the extent permitted by applicable law. ... If you want to reproduce or use content ... in any manner other than as described above, including for purposes of developing or training AI or to conduct computer analysis, you will need Merriam-Webster's permission."
The reproduction, redistribution, modification or publication of any part of the Services without the express written consent of Pearson and/or its licensors is strictly prohibited.
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