dictionaryCall.js

data = null;
xhr = null;
xhr = new XMLHttpRequest();
xhr.withCredentials = true;
xhr.addEventListener("readystatechange", function () {
  if (this.readyState === this.DONE) {
    jsonText = JSON.parse(xhr.responseText);
    wordDefinition = jsonText.results[0].lexicalEntries[0].entries[0].senses[0].subsenses[0].definitions[0];
    console.log(jsonText.results[0].lexicalEntries[0].entries[0].senses[0].subsenses[0].definitions[0]);
  }
});
xhr.open("GET", "https://od-api.oxforddictionaries.com:443/api/v1/entries/en/"+wordToSearch+'/definitions', false);
xhr.setRequestHeader("accept", "application/json");
xhr.setRequestHeader("app_id", "xxxx");
xhr.setRequestHeader("app_key", "xxxx");
xhr.send(data);