Synonyms of securely

2 Syllables
staunchly, stoutly, stably, greatly, fully, strongly, tightly, firmly
3 Syllables
robustly, steadily, forcibly, sturdily, mightily, heavily, durably, heartily, solidly
4 Syllables
actively, invincibly, unshakeably, vigorously, completely, decidedly
5 Syllables
resolutely, indomitably
6 Syllables
energetically