1. a flat paper container with a sealable flap, used to enclose a letter or document
2. a covering or containing structure or layer

1. to wrap up, cover, or surround completely

Examples

• She sealed the letter in a white envelope.
• Please address the envelope clearly.
• The virus has a protective envelope around its core.
• Fog enveloped the entire city.
• The mountains were enveloped in clouds.
• He enveloped her in a warm hug.
• The building was enveloped in flames.