Just a general reusable solution:

function Replace-String {
    [CmdletBinding()][OutputType([string])] param(
        [Parameter(Mandatory = $True, ValueFromPipeLine = $True)]$InputObject,
        [Parameter(Mandatory = $True, Position = 0)][Array]$Pair,
        [Alias('CaseSensitive')][switch]$MatchCase
    )
    for ($i = 0; $i -lt $Pair.get_Count()) {
        if ($Pair[$i] -is [Array]) {
            $InputObject = $InputObject |Replace-String -MatchCase:$MatchCase $Pair[$i++]
        }
        else {
            $Regex = $Pair[$i++]
            $Substitute = if ($i -lt $Pair.get_Count() -and $Pair[$i] -isnot [Array]) { $Pair[$i++] }
            if ($MatchCase) { $InputObject = $InputObject -cReplace $Regex, $Substitute }
            else            { $InputObject = $InputObject -iReplace $Regex, $Substitute }
        }
    }
    $InputObject
}; Set-Alias Replace Replace-String

Usage:

$lookupTable |Replace 'something1', 'something1aa', 'something2', 'something2bb', 'something3', 'something3cc'

or:

$lookupTable |Replace ('something1', 'something1aa'), ('something2', 'something2bb'), ('something3', 'something3cc')

Example:

'hello world' |Replace ('h','H'), ' ', ('w','W')
HelloWorld