Stealthily
/ˈstelθɪli/
Definition 1 of 2
Pro Tip 1/3Secret Intent
Used when the action is intentional to avoid drawing attention. 
She stealthily hid the gift, hoping it would be a surprise.
Pro Tip 2/3Physical Quietness
Often involves moving silently or with minimal noise. 
He opened the door stealthily to avoid being heard.
Pro Tip 3/3Narrative Tension
Use to create suspense in stories or descriptions. 
The thief stealthily approached the safe, every second pulsing with tension.