1. ripen and generate pus

e.g. her wounds are festering

Synonym: festersuppurate

2. grow old or older

e.g. She aged gracefully
we age every day--what a depressing thought!
Young men senesce

Synonym: senesceageget onmature

3. develop and reach maturity
undergo maturation

e.g. He matured fast
The child grew fast

Synonym: maturegrow