Definition of "gerund"

gerund

/ˈd͡ʒɛɹənd/

noun
plural gerunds
1. (grammar) A verbal form that functions as a verbal noun. (In English, a gerund has the same spelling as a present participle, but functions differently; however, this distinction may be ambiguous or unclear and so is no longer made in some modern texts such as A Comprehensive Grammar of the English Language and The Cambridge Grammar of the English Language)
  Quotations
  Compounds in which gerunds are the second element look exactly like compounds in which present participles are the second element, but different principles of hyphenation apply.
  1991, Edward Johnson, The Handbook of Good English, page 208
  Like any noun, the gerund functions as a subject, direct object, indirect object, object of the preposition, or predicate nominative. The gerund phrase is made up of the present participle ("-ing") and can contain an object and/or a modifier (and sometimes many modifiers). The gerund is a verbal noun.
  2002, Dan Mulvey, Grammar the Easy Way, page 25
  Gerunds and gerund phrases are always nouns, so they are always predicate nominatives when used as complements. Do be careful to distinguish progressive-tense verbs from gerunds used as subjective complements.
  2005, Gary Lutz, Diane Stevenson, The Writer's Digest Grammar Desk Reference, page 55
2. (grammar) In some languages such as Dutch, Italian or Russian, a verbal form similar to a present participle, but functioning as an adverb to form adverbial phrases or continuous tense. These constructions have various names besides gerund, depending on the language, such as conjunctive participles, active participles, adverbial participles, transgressives, etc.
  Quotations
  The Spanish gerund is quite unlike the English -ing form (‘walking’, ‘replying’, ‘saying’, etc.), which can function as a gerund, a present participle, a noun or an adjective; and it is also unlike the French form ending in -ant, which covers the functions of both the Spanish gerund and the adjectival form in -ante, -(i)ente discussed at 19.4.
  2013, John Butt, Carmen Benjamin, A New Reference Grammar of Modern Spanish, Kindle edition, Routledge