Merriam-Webster rigor rigor Merriam-Webster rigor definitions "rigor" Merriam-Webster rigor Merriam-Webster rigor rigor Mirriam-Webster Online Dictionary "rigor" merriam-webster.com Merriam-Webster Merriam-Webster Merriam-Webster dictionary Mirriam-Webster Online Dictionary merriam-webster.com and literal denotation "rigor" "rigor" first definition offered in the Merriam Webster Dictionary definitions