infinitive

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A verb form that functions as a substantive while retaining certain verbal characteristics, such as modification by adverbs, and that in English may be preceded by to, as in To go willingly is to show strength or We want him to work harder, or may also occur without to, as in She had them read the letter or We may finish today. See Usage Note at split infinitive.

Century Dictionary and Cyclopedia

1. In grammar, unlimited; indefinite: noting a certain verb-form sometimes called the infinitive mode. See II.
2. n. In grammar, a certain verb-form expressing the general sense of the verb without restriction in regard to person or number, as English give, German geben, French donner, Latin dare, Greek διδόναι. In the grammar of Latin and of the most familiar modern languages, it is used as the representative form of the whole verb-system. It is by origin simply a verbal noun in an oblique case (oftenest dative); and hence its tendency to use with a stereo-typed prefixed preposition, as to in English, zu(= English to) in German, at (= English at) in Scandinavian, de (‘of’) or à (‘to’) in French, and so on; but the preposition is no part of the infinitive. In the old grammars, and in many recent ones, it is called a mode; but the term is objectionable, and is going out of use. Abbreviated infinitive
3. n. An endless quantity or number; an infinity.
4. n. a name conveniently used to designate briefly the infinitive phrase consisting of the infinitive proper (for example, ‘designate,’ below) and the so-called ‘sign,’ the preposition ‘to,’ when separated by a qualifying adverb or phrase, as in ‘to briefly designate,’ ‘to readily understand,’ ‘to suddenly and completely change one's attitude.’ This use is in high disfavor with literary critics and purists who write upon the subject, but it occurs abundantly in English literature from the seventeenth century down. Nearly every ‘standard author’ is ‘guilty’ of it, as Fitzedward Hall and others have shown, and it is thoroughly established in popular speech. It is often dictated by a sense of rhythm, the placing of the adverb after the verb and before the week adjunct or object which follows the verb resulting often in disharmony of rhythm and stress. The idiom is a perfectly natural development of the conditions given—a verb to be qualified, a stress qualifier, and an unstressed syllable (to) of no definite meaning. This syllable to is instinctively treated as a or the is treated in a similarly stressed sequence of adjective and noun (‘a brief designation,’ ‘the proper order,’ etc.)

Wiktionary

1. n. grammar The uninflected form of verb. In English, this is usually formed with the verb stem preceded by 'to'. e.g. 'to sit'
2. n. grammar A verbal noun formed from the infinitive of a verb
3. adj. grammar Formed with the infinitive

GNU Webster's 1913

1. n. Unlimited; not bounded or restricted; undefined.
2. n. (Gram.) An infinitive form of verb; a verb in the infinitive mood; the infinitive mood.
3. adv. (Gram.) In the manner of an infinitive mood.

WordNet 3.0

1. n. the uninflected form of verb