first floorn.1. The ground floor of a building.2. Chiefly British The floor immediately above the ground floor.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.first floor n 1. Brit the floor or storey of a building immediately above the ground floor. US and Canadian term: second floor 2. US and Canadian another term for ground floor Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014first? floor? n. 1. the ground floor of a building. 2. Chiefly Brit. the floor next above the ground floor of a building. [1655?65] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.ground floor – first floorIn British English, the floor of a building which is level with the ground is called the ground floor. The floor above it is called the first floor, the floor above that is the second floor, and so on.In American English, the floor which is level with the ground is called the first floor, the floor above it is the second floor, and so on.