Somewhat mild, not very strong in flavor or effect.
Semimild means not too strong, kind of gentle.
Examples:
The sauce is semimild, not too spicy.
I like semimild tea, not too strong.
The medicine is semimild, it won't make you feel bad.
The cat's meow was semimild, not too loud.
The superhero's powers were semimild, not very strong.
The semimild wind blew softly through the trees.