urban_module_hook.php

<?php

function urban_module_node_presave(NodeInterface $node) {
  if ($node->bundle() == 'urban_definition') {
    /** @var \Drupal\urban_module\Service\UrbanDictionaryService $ubService */
    $ubService = \Drupal::service('urban_module.service');
    $definition = $ubService->getDefinition($node->getTitle());
    if (!empty($definition)) {
      $node->title->value = $definition->getTerm();
      $node->field_definition->value = $definition->getDefinition();
      $node->field_example->value = $definition->getExample();
    }
  }
}