Youthfully

adv.energetic, joyfulwarm

What it means

With freshness, energy, playfulness, or openness associated with youth.

Reach for it when describing a manner while avoiding the claim that only young people show it

He approached the unfamiliar game youthfully and without self-consciousness.

everyday
energetically
when visible activity is the actual manner
not when Energetically can be frantic and should not be treated as proof of youthfulness.
warm
openly
when lack of defensiveness or self-consciousness is central
not when Openness occurs at every age and may not feel youthful.
warm
playfully
when lighthearted engagement matters
not when Playfulness is one quality and does not capture youthful freshness more broadly.
professional
curiously
when questioning and desire to learn are the evidence
not when Curiously can also mean strangely and says nothing about age.
literary
freshly
when a new, unwearied approach is central
not when Freshly more often means recently and can sound awkward for a person's manner.
literary
sprightly
when lively movement suits an old-fashioned voice
not when Sprightly is normally an adjective and can patronize older adults.

youthfully curious
She remained youthfully curious while bringing decades of judgment.
youthfully energetic
The ensemble played youthfully energetic music without rushing.
smile youthfully
He could smile youthfully without disguising his age.

Youthfully is uncommon and can be ageist. A specific adverb such as playfully, curiously, or energetically is usually clearer.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.