Science, Tech, Math › Science Definition of Alkaline in Chemstry It's an aqueous solution with a pH greater than 7 Share Flipboard Email Print Glass beakers indicating blue for weak alkaline level, green for strong alkali level, and red for weak acidity level. Trish Gant / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 13, 2019 Alkaline refers to an aqueous solution having a pH greater than 7 or a [OH-] greater than 10-7. An alkaline solution is also known as basic.