Definitions of weak:

• adjective:   lacking physical strength or vigor
• adjective:   used of verbs having standard (or regular) inflection
• adjective:   having little physical or spiritual strength

  Example: "A weak radio signal"

• adjective:   lacking power
• adjective:   characterized by excessive softness or self-indulgence
• adjective:   used of vowels or syllables; pronounced with little or no stress

  Example: "A weak stress on the second syllable"

• adjective:   overly diluted; thin and insipid

  Example: "Weak tea"

• adjective:   lacking force; feeble
• adjective:   having the attributes of man as opposed to e.g. divine beings
• adjective:   lacking physical strength or vitality