A legendary sea creature having the head and upper body of a man and the tail of a fish.(noun)
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.
Use "merman" in a sentence
"We are told in one place a few lines further on that the merman is of humankind; and in another that he is a kind of fish (Night dccccxlv)."
"I'm from Earth but I'm what your people would call a merman."
"The merman was the first to see the importance of uniting the continent of Otaria, saving its fragmented history."