To be on guard against; be cautious of: "Beware the ides of March” ( Shakespeare).
To be cautious; exert caution: We had to beware of the icy patches on the road. Beware of the dog.
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.