DICTIONARIES
Monolingual: English definition
Longman Dictionary of Contemporary English
Macmillan Dictionary
Oxford Learner's Dictionaries
Lexico.com (Oxford)
Cambridge Dictionaries Online
Collins English Dictionary
Merriam-Webster
OTHER DICTIONARIES
Online Etymology Dictionary
Online Oxford Collocation Dictionary
English-Spanish/ Spanish-English bilingual dictionaries
Collins Spanish English Dictionary
Cambridge English-Spanish
Lexico.com English-Spanish
Word Reference English Spanish
Translation Sites
Linguee.es
Reverso