movable
adj.able to be moved from one place to another. You use this to describe things that are not fixed or stuck in one spot.
adj.capable of being moved or relocated; not fixed in a permanent position. Often used to describe physical objects or scheduled dates that can be adjusted.
“The office has movable walls to change the room size.”
“The festival is a movable event that takes place on a different weekend every year depending on the weather.”
“In the history of printing, the invention of movable type allowed for the rapid mass production of books, fundamentally altering the spread of information across the continent.”
Typically used attributively before a noun. When referring to holidays like Easter, the phrase 'movable feast' is a standard collocation.
From Old French movable. By surface analysis, move + -able.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.