Quick definitions from WordNet (harmless)
▸ adjective: unlikely to harm or disturb anyone ("Harmless old man")
▸ adjective: not producing any toxic effects
▸ adjective: not threatening to life or health; not malignant ("A benign tumor is usually harmless")
▸ adjective: not causing or capable of causing harm ("Harmless bacteria")
▸ adjective: not injurious to physical or mental health
▸ Also see harmless
▸ adjective: unlikely to harm or disturb anyone ("Harmless old man")
▸ adjective: not producing any toxic effects
▸ adjective: not threatening to life or health; not malignant ("A benign tumor is usually harmless")
▸ adjective: not causing or capable of causing harm ("Harmless bacteria")
▸ adjective: not injurious to physical or mental health
▸ Also see harmless