Defective verb

From Tomísimo

A defective verb is a verb that isn't used in all its theoretically possible conjugations.

Verbs conjugated only in the third person singular

Some defective verbs are only used in the third person singular since that is the only logical use for them. Most verbs relating the weather fall into this category. For example: llover, anochecer, amanecer, granizar, helar, and nevar.

Gustar-like verbs

Gustar and other verbs like it are commonly used only in the third person singular and plural, but they are not truly defective, since in some cases they are used in other conjugations as well.

Soler

The verb soler is usually not conjugated in the preterit, conditional, or future tenses.

Certain -ir verbs

A few verbs ending in ir are only used in conjugations where the verb ending starts with 'i'. Verbs in this category are: abolir, agredir, balbucir, and blandir.

Verbs only used in the infinitive and past participle

There is another handful of verbs that are normally only used in the infinitive and past participle forms, when used at all. These verbs aren't all that common. despavorir, empedernir, aterirse, and desolar.