verb - to improve a skill, technique, or ability by practicing it regularly
adjective, American English, informal - having too much air in the stomach
noun - a substance or material that allows electricity to pass through it under some conditions but not under others, used especially in electronic devices
adjective, formal - matching something in size, degree, or importance; appropriate in relation to something else
noun, technical - a serious mental condition in which a person gradually loses the ability to think, remember, and behave normally, usually because of disease or old age