faltar
to be missing
fault
an imperfection or lack
+
-ar
verb suffix
Faltar means to be missing and can be thought of as fault0 + -ar1, where something with a fault or lack0 is missing something, and -ar1 makes it a verb.
verb
  1. to be missing
    To be missing or lacking
    Me falta un ingrediente para la receta. // I'm missing an ingredient for the recipe.