Spanish Dictionaries to use (castellano)
Spanish only (and the most official resource): El Diccionario de la lengua española - Real Academia Española
dle.rae.es
Spanish-English:
Cambridge Dictionary
https://dictionary.cambridge.org/dictionary/spanish-english/
English-Spanish/Spanish-English:
SpanishDictionary
https://www.spanishdict.com
English-Spanish/Spanish-English:
Linguee
https://www.linguee.es/
English-Spanish/Spanish-English:
Collins Dictionary
https://www.collinsdictionary.com/dictionary/english-spanish