Portuguese
A large number of Portuguese verbs are defective in person, i.e., they lack the proper form for one of the pronouns in some tense. The verb colorir ("to color") has no first-person singular in the present (thus requiring a paraphrase, like estou colorindo ("I am coloring") or the use of another verb of similar meaning, like pintar ("to paint").
Read more about this topic: Defective Verb